
import {
  Blob,
  btoa,
  createImageBitmap,
  CSSStyleDeclaration,
  performance,
  document,
  DOMParser,
  EventTarget,
  fetch,
  Headers,
  HTMLCanvasElement,
Image,
  HTMLImageElement,
  ImageBitmap,
  location,
  navigator,
  Request,
  requestAnimationFrame,
  cancelAnimationFrame,
  Response,
  URL,
  window,
  self,
  WebAssembly,
  Worker,
  XMLHttpRequest,
ImageData,
  core
  } from 'dhtml-weixin';
  import TextDecoder from "../../3rd/textDecoder/TextDecoder"
  import {
    AnimationClip,
    Bone,
    Box3,
    BufferAttribute,
    BufferGeometry,
    ClampToEdgeWrapping,
    Color,
    ColorManagement,
    DirectionalLight,
    DoubleSide,
    FileLoader,
    FrontSide,
    Group,
    ImageBitmapLoader,
    InstancedMesh,
    InterleavedBuffer,
    InterleavedBufferAttribute,
    Interpolant,
    InterpolateDiscrete,
    InterpolateLinear,
    Line,
    LineBasicMaterial,
    LineLoop,
    LineSegments,
    LinearFilter,
    LinearMipmapLinearFilter,
    LinearMipmapNearestFilter,
    LinearSRGBColorSpace,
    Loader,
    LoaderUtils,
    Material,
    MathUtils,
    Matrix4,
    Mesh,
    MeshBasicMaterial,
    MeshPhysicalMaterial,
    MeshStandardMaterial,
    MirroredRepeatWrapping,
    NearestFilter,
    NearestMipmapLinearFilter,
    NearestMipmapNearestFilter,
    NumberKeyframeTrack,
    Object3D,
    OrthographicCamera,
    PerspectiveCamera,
    PointLight,
    Points,
    PointsMaterial,
    PropertyBinding,
    Quaternion,
    QuaternionKeyframeTrack,
    RepeatWrapping,
    Skeleton,
    SkinnedMesh,
    Sphere,
    SpotLight,
    Texture,
    TextureLoader,
    TriangleFanDrawMode,
    TriangleStripDrawMode,
    Vector2,
    Vector3,
    VectorKeyframeTrack,
    SRGBColorSpace,
    InstancedBufferAttribute
  } from '../../Three';
  import { toTrianglesDrawMode } from '../utils/BufferGeometryUtils.js';
  
  class GLTFLoader extends Loader {
  
    constructor( manager ) {
  
      super( manager );
  
      this.dracoLoader = null;
      this.ktx2Loader = null;
      this.meshoptDecoder = null;
  
      this.pluginCallbacks = [];
  
      this.register( function ( parser ) {
  
        return new GLTFMaterialsClearcoatExtension( parser );
  
      } );
  
      this.register( function ( parser ) {
  
        return new GLTFTextureBasisUExtension( parser );
  
      } );
  
      this.register( function ( parser ) {
  
        return new GLTFTextureWebPExtension( parser );
  
      } );
  
      this.register( function ( parser ) {
  
        return new GLTFTextureAVIFExtension( parser );
  
      } );
  
      this.register( function ( parser ) {
  
        return new GLTFMaterialsSheenExtension( parser );
  
      } );
  
      this.register( function ( parser ) {
  
        return new GLTFMaterialsTransmissionExtension( parser );
  
      } );
  
      this.register( function ( parser ) {
  
        return new GLTFMaterialsVolumeExtension( parser );
  
      } );
  
      this.register( function ( parser ) {
  
        return new GLTFMaterialsIorExtension( parser );
  
      } );
  
      this.register( function ( parser ) {
  
        return new GLTFMaterialsEmissiveStrengthExtension( parser );
  
      } );
  
      this.register( function ( parser ) {
  
        return new GLTFMaterialsSpecularExtension( parser );
  
      } );
  
      this.register( function ( parser ) {
  
        return new GLTFMaterialsIridescenceExtension( parser );
  
      } );
  
      this.register( function ( parser ) {
  
        return new GLTFMaterialsAnisotropyExtension( parser );
  
      } );
  
      this.register( function ( parser ) {
  
        return new GLTFLightsExtension( parser );
  
      } );
  
      this.register( function ( parser ) {
  
        return new GLTFMeshoptCompression( parser );
  
      } );
  
      this.register( function ( parser ) {
  
        return new GLTFMeshGpuInstancing( parser );
  
      } );
  
    }
  
    load( url, onLoad, onProgress, onError ) {
  
      const scope = this;
  
      let resourcePath;
  
      if ( this.resourcePath !== '' ) {
  
        resourcePath = this.resourcePath;
  
      } else if ( this.path !== '' ) {
  
        resourcePath = this.path;
  
      } else {
  
        resourcePath = LoaderUtils.extractUrlBase( url );
  
      }
  
      // Tells the LoadingManager to track an extra item, which resolves after
      // the model is fully loaded. This means the count of items loaded will
      // be incorrect, but ensures manager.onLoad() does not fire early.
      this.manager.itemStart( url );
  
      const _onError = function ( e ) {
  
        if ( onError ) {
  
          onError( e );
  
        } else {
  
          console.error( e );
  
        }
  
        scope.manager.itemError( url );
        scope.manager.itemEnd( url );
  
      };
  
      const loader = new FileLoader( this.manager );
  
      loader.setPath( this.path );
      loader.setResponseType( 'arraybuffer' );
      loader.setRequestHeader( this.requestHeader );
      loader.setWithCredentials( this.withCredentials );
  
      loader.load( url, function ( data ) {
  
        try {
  
          scope.parse( data, resourcePath, function ( gltf ) {
  
            onLoad( gltf );
  
            scope.manager.itemEnd( url );
  
          }, _onError );
  
        } catch ( e ) {
  
          _onError( e );
  
        }
  
      }, onProgress, _onError );
  
    }
  
    setDRACOLoader( dracoLoader ) {
  
      this.dracoLoader = dracoLoader;
      return this;
  
    }
  
    setDDSLoader() {
  
      throw new Error(
  
        'THREE.GLTFLoader: "MSFT_texture_dds" no longer supported. Please update to "KHR_texture_basisu".'
  
      );
  
    }
  
    setKTX2Loader( ktx2Loader ) {
  
      this.ktx2Loader = ktx2Loader;
      return this;
  
    }
  
    setMeshoptDecoder( meshoptDecoder ) {
  
      this.meshoptDecoder = meshoptDecoder;
      return this;
  
    }
  
    register( callback ) {
  
      if ( this.pluginCallbacks.indexOf( callback ) === - 1 ) {
  
        this.pluginCallbacks.push( callback );
  
      }
  
      return this;
  
    }
  
    unregister( callback ) {
  
      if ( this.pluginCallbacks.indexOf( callback ) !== - 1 ) {
  
        this.pluginCallbacks.splice( this.pluginCallbacks.indexOf( callback ), 1 );
  
      }
  
      return this;
  
    }
  
    parse( data, path, onLoad, onError ) {
  
      let json;
      const extensions = {};
      const plugins = {};
      const textDecoder = new TextDecoder();
  
      if ( typeof data === 'string' ) {
  
        json = JSON.parse( data );
  
      } else if ( data instanceof ArrayBuffer ) {
  
        const magic = textDecoder.decode( new Uint8Array( data, 0, 4 ) );
  
        if ( magic === BINARY_EXTENSION_HEADER_MAGIC ) {
  
          try {
  
            extensions[ EXTENSIONS.KHR_BINARY_GLTF ] = new GLTFBinaryExtension( data );
  
          } catch ( error ) {
  
            if ( onError ) onError( error );
            return;
  
          }
  
          json = JSON.parse( extensions[ EXTENSIONS.KHR_BINARY_GLTF ].content );
  
        } else {
  const text = textDecoder.decode( data )
          json = JSON.parse(text );
  
        }
  
      } else {
  
        json = data;
  
      }
  
      if ( json.asset === undefined || json.asset.version[ 0 ] < 2 ) {
  
        if ( onError ) onError( new Error( 'THREE.GLTFLoader: Unsupported asset. glTF versions >=2.0 are supported.' ) );
        return;
  
      }
  
      const parser = new GLTFParser( json, {
  
        path: path || this.resourcePath || '',
        crossOrigin: this.crossOrigin,
        requestHeader: this.requestHeader,
        manager: this.manager,
        ktx2Loader: this.ktx2Loader,
        meshoptDecoder: this.meshoptDecoder
  
      } );
  
      parser.fileLoader.setRequestHeader( this.requestHeader );
  
      for ( let i = 0; i < this.pluginCallbacks.length; i ++ ) {
  
        const plugin = this.pluginCallbacks[ i ]( parser );
  
        if ( ! plugin.name ) console.error( 'THREE.GLTFLoader: Invalid plugin found: missing name' );
  
        plugins[ plugin.name ] = plugin;
  
        // Workaround to avoid determining as unknown extension
        // in addUnknownExtensionsToUserData().
        // Remove this workaround if we move all the existing
        // extension handlers to plugin system
        extensions[ plugin.name ] = true;
  
      }
  
      if ( json.extensionsUsed ) {
  
        for ( let i = 0; i < json.extensionsUsed.length; ++ i ) {
  
          const extensionName = json.extensionsUsed[ i ];
          const extensionsRequired = json.extensionsRequired || [];
  
          switch ( extensionName ) {
  
            case EXTENSIONS.KHR_MATERIALS_UNLIT:
              extensions[ extensionName ] = new GLTFMaterialsUnlitExtension();
              break;
  
            case EXTENSIONS.KHR_DRACO_MESH_COMPRESSION:
              extensions[ extensionName ] = new GLTFDracoMeshCompressionExtension( json, this.dracoLoader );
              break;
  
            case EXTENSIONS.KHR_TEXTURE_TRANSFORM:
              extensions[ extensionName ] = new GLTFTextureTransformExtension();
              break;
  
            case EXTENSIONS.KHR_MESH_QUANTIZATION:
              extensions[ extensionName ] = new GLTFMeshQuantizationExtension();
              break;
  
            default:
  
              if ( extensionsRequired.indexOf( extensionName ) >= 0 && plugins[ extensionName ] === undefined ) {
  
                console.warn( 'THREE.GLTFLoader: Unknown extension "' + extensionName + '".' );
  
              }
  
          }
  
        }
  
      }
  
      parser.setExtensions( extensions );
      parser.setPlugins( plugins );
      parser.parse( onLoad, onError );
  
    }
  
    parseAsync( data, path ) {
  
      const scope = this;
  
      return new Promise( function ( resolve, reject ) {
  
        scope.parse( data, path, resolve, reject );
  
      } );
  
    }
  
  }
  
  /* GLTFREGISTRY */
  
  function GLTFRegistry() {
  
    let objects = {};
  
    return	{
  
      get: function ( key ) {
  
        return objects[ key ];
  
      },
  
      add: function ( key, object ) {
  
        objects[ key ] = object;
  
      },
  
      remove: function ( key ) {
  
        delete objects[ key ];
  
      },
  
      removeAll: function () {
  
        objects = {};
  
      }
  
    };
  
  }
  
  /*********************************/
  /********** EXTENSIONS ***********/
  /*********************************/
  
  const EXTENSIONS = {
    KHR_BINARY_GLTF: 'KHR_binary_glTF',
    KHR_DRACO_MESH_COMPRESSION: 'KHR_draco_mesh_compression',
    KHR_LIGHTS_PUNCTUAL: 'KHR_lights_punctual',
    KHR_MATERIALS_CLEARCOAT: 'KHR_materials_clearcoat',
    KHR_MATERIALS_IOR: 'KHR_materials_ior',
    KHR_MATERIALS_SHEEN: 'KHR_materials_sheen',
    KHR_MATERIALS_SPECULAR: 'KHR_materials_specular',
    KHR_MATERIALS_TRANSMISSION: 'KHR_materials_transmission',
    KHR_MATERIALS_IRIDESCENCE: 'KHR_materials_iridescence',
    KHR_MATERIALS_ANISOTROPY: 'KHR_materials_anisotropy',
    KHR_MATERIALS_UNLIT: 'KHR_materials_unlit',
    KHR_MATERIALS_VOLUME: 'KHR_materials_volume',
    KHR_TEXTURE_BASISU: 'KHR_texture_basisu',
    KHR_TEXTURE_TRANSFORM: 'KHR_texture_transform',
    KHR_MESH_QUANTIZATION: 'KHR_mesh_quantization',
    KHR_MATERIALS_EMISSIVE_STRENGTH: 'KHR_materials_emissive_strength',
    EXT_TEXTURE_WEBP: 'EXT_texture_webp',
    EXT_TEXTURE_AVIF: 'EXT_texture_avif',
    EXT_MESHOPT_COMPRESSION: 'EXT_meshopt_compression',
    EXT_MESH_GPU_INSTANCING: 'EXT_mesh_gpu_instancing'
  };
  
  /**
   * Punctual Lights Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_lights_punctual
   */
  class GLTFLightsExtension {
  
    constructor( parser ) {
  
      this.parser = parser;
      this.name = EXTENSIONS.KHR_LIGHTS_PUNCTUAL;
  
      // Object3D instance caches
      this.cache = { refs: {}, uses: {} };
  
    }
  
    _markDefs() {
  
      const parser = this.parser;
      const nodeDefs = this.parser.json.nodes || [];
  
      for ( let nodeIndex = 0, nodeLength = nodeDefs.length; nodeIndex < nodeLength; nodeIndex ++ ) {
  
        const nodeDef = nodeDefs[ nodeIndex ];
  
        if ( nodeDef.extensions
            && nodeDef.extensions[ this.name ]
            && nodeDef.extensions[ this.name ].light !== undefined ) {
  
          parser._addNodeRef( this.cache, nodeDef.extensions[ this.name ].light );
  
        }
  
      }
  
    }
  
    _loadLight( lightIndex ) {
  
      const parser = this.parser;
      const cacheKey = 'light:' + lightIndex;
      let dependency = parser.cache.get( cacheKey );
  
      if ( dependency ) return dependency;
  
      const json = parser.json;
      const extensions = ( json.extensions && json.extensions[ this.name ] ) || {};
      const lightDefs = extensions.lights || [];
      const lightDef = lightDefs[ lightIndex ];
      let lightNode;
  
      const color = new Color( 0xffffff );
  
      if ( lightDef.color !== undefined ) color.setRGB( lightDef.color[ 0 ], lightDef.color[ 1 ], lightDef.color[ 2 ], LinearSRGBColorSpace );
  
      const range = lightDef.range !== undefined ? lightDef.range : 0;
  
      switch ( lightDef.type ) {
  
        case 'directional':
          lightNode = new DirectionalLight( color );
          lightNode.target.position.set( 0, 0, - 1 );
          lightNode.add( lightNode.target );
          break;
  
        case 'point':
          lightNode = new PointLight( color );
          lightNode.distance = range;
          break;
  
        case 'spot':
          lightNode = new SpotLight( color );
          lightNode.distance = range;
          // Handle spotlight properties.
          lightDef.spot = lightDef.spot || {};
          lightDef.spot.innerConeAngle = lightDef.spot.innerConeAngle !== undefined ? lightDef.spot.innerConeAngle : 0;
          lightDef.spot.outerConeAngle = lightDef.spot.outerConeAngle !== undefined ? lightDef.spot.outerConeAngle : Math.PI / 4.0;
          lightNode.angle = lightDef.spot.outerConeAngle;
          lightNode.penumbra = 1.0 - lightDef.spot.innerConeAngle / lightDef.spot.outerConeAngle;
          lightNode.target.position.set( 0, 0, - 1 );
          lightNode.add( lightNode.target );
          break;
  
        default:
          throw new Error( 'THREE.GLTFLoader: Unexpected light type: ' + lightDef.type );
  
      }
  
      // Some lights (e.g. spot) default to a position other than the origin. Reset the position
      // here, because node-level parsing will only override position if explicitly specified.
      lightNode.position.set( 0, 0, 0 );
  
      lightNode.decay = 2;
  
      assignExtrasToUserData( lightNode, lightDef );
  
      if ( lightDef.intensity !== undefined ) lightNode.intensity = lightDef.intensity;
  
      lightNode.name = parser.createUniqueName( lightDef.name || ( 'light_' + lightIndex ) );
  
      dependency = Promise.resolve( lightNode );
  
      parser.cache.add( cacheKey, dependency );
  
      return dependency;
  
    }
  
    getDependency( type, index ) {
  
      if ( type !== 'light' ) return;
  
      return this._loadLight( index );
  
    }
  
    createNodeAttachment( nodeIndex ) {
  
      const self = this;
      const parser = this.parser;
      const json = parser.json;
      const nodeDef = json.nodes[ nodeIndex ];
      const lightDef = ( nodeDef.extensions && nodeDef.extensions[ this.name ] ) || {};
      const lightIndex = lightDef.light;
  
      if ( lightIndex === undefined ) return null;
  
      return this._loadLight( lightIndex ).then( function ( light ) {
  
        return parser._getNodeRef( self.cache, lightIndex, light );
  
      } );
  
    }
  
  }
  
  /**
   * Unlit Materials Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_unlit
   */
  class GLTFMaterialsUnlitExtension {
  
    constructor() {
  
      this.name = EXTENSIONS.KHR_MATERIALS_UNLIT;
  
    }
  
    getMaterialType() {
  
      return MeshBasicMaterial;
  
    }
  
    extendParams( materialParams, materialDef, parser ) {
  
      const pending = [];
  
      materialParams.color = new Color( 1.0, 1.0, 1.0 );
      materialParams.opacity = 1.0;
  
      const metallicRoughness = materialDef.pbrMetallicRoughness;
  
      if ( metallicRoughness ) {
  
        if ( Array.isArray( metallicRoughness.baseColorFactor ) ) {
  
          const array = metallicRoughness.baseColorFactor;
  
          materialParams.color.setRGB( array[ 0 ], array[ 1 ], array[ 2 ], LinearSRGBColorSpace );
          materialParams.opacity = array[ 3 ];
  
        }
  
        if ( metallicRoughness.baseColorTexture !== undefined ) {
  
          pending.push( parser.assignTexture( materialParams, 'map', metallicRoughness.baseColorTexture, SRGBColorSpace ) );
  
        }
  
      }
  
      return Promise.all( pending );
  
    }
  
  }
  
  /**
   * Materials Emissive Strength Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/blob/5768b3ce0ef32bc39cdf1bef10b948586635ead3/extensions/2.0/Khronos/KHR_materials_emissive_strength/README.md
   */
  class GLTFMaterialsEmissiveStrengthExtension {
  
    constructor( parser ) {
  
      this.parser = parser;
      this.name = EXTENSIONS.KHR_MATERIALS_EMISSIVE_STRENGTH;
  
    }
  
    extendMaterialParams( materialIndex, materialParams ) {
  
      const parser = this.parser;
      const materialDef = parser.json.materials[ materialIndex ];
  
      if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {
  
        return Promise.resolve();
  
      }
  
      const emissiveStrength = materialDef.extensions[ this.name ].emissiveStrength;
  
      if ( emissiveStrength !== undefined ) {
  
        materialParams.emissiveIntensity = emissiveStrength;
  
      }
  
      return Promise.resolve();
  
    }
  
  }
  
  /**
   * Clearcoat Materials Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_clearcoat
   */
  class GLTFMaterialsClearcoatExtension {
  
    constructor( parser ) {
  
      this.parser = parser;
      this.name = EXTENSIONS.KHR_MATERIALS_CLEARCOAT;
  
    }
  
    getMaterialType( materialIndex ) {
  
      const parser = this.parser;
      const materialDef = parser.json.materials[ materialIndex ];
  
      if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) return null;
  
      return MeshPhysicalMaterial;
  
    }
  
    extendMaterialParams( materialIndex, materialParams ) {
  
      const parser = this.parser;
      const materialDef = parser.json.materials[ materialIndex ];
  
      if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {
  
        return Promise.resolve();
  
      }
  
      const pending = [];
  
      const extension = materialDef.extensions[ this.name ];
  
      if ( extension.clearcoatFactor !== undefined ) {
  
        materialParams.clearcoat = extension.clearcoatFactor;
  
      }
  
      if ( extension.clearcoatTexture !== undefined ) {
  
        pending.push( parser.assignTexture( materialParams, 'clearcoatMap', extension.clearcoatTexture ) );
  
      }
  
      if ( extension.clearcoatRoughnessFactor !== undefined ) {
  
        materialParams.clearcoatRoughness = extension.clearcoatRoughnessFactor;
  
      }
  
      if ( extension.clearcoatRoughnessTexture !== undefined ) {
  
        pending.push( parser.assignTexture( materialParams, 'clearcoatRoughnessMap', extension.clearcoatRoughnessTexture ) );
  
      }
  
      if ( extension.clearcoatNormalTexture !== undefined ) {
  
        pending.push( parser.assignTexture( materialParams, 'clearcoatNormalMap', extension.clearcoatNormalTexture ) );
  
        if ( extension.clearcoatNormalTexture.scale !== undefined ) {
  
          const scale = extension.clearcoatNormalTexture.scale;
  
          materialParams.clearcoatNormalScale = new Vector2( scale, scale );
  
        }
  
      }
  
      return Promise.all( pending );
  
    }
  
  }
  
  /**
   * Iridescence Materials Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_iridescence
   */
  class GLTFMaterialsIridescenceExtension {
  
    constructor( parser ) {
  
      this.parser = parser;
      this.name = EXTENSIONS.KHR_MATERIALS_IRIDESCENCE;
  
    }
  
    getMaterialType( materialIndex ) {
  
      const parser = this.parser;
      const materialDef = parser.json.materials[ materialIndex ];
  
      if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) return null;
  
      return MeshPhysicalMaterial;
  
    }
  
    extendMaterialParams( materialIndex, materialParams ) {
  
      const parser = this.parser;
      const materialDef = parser.json.materials[ materialIndex ];
  
      if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {
  
        return Promise.resolve();
  
      }
  
      const pending = [];
  
      const extension = materialDef.extensions[ this.name ];
  
      if ( extension.iridescenceFactor !== undefined ) {
  
        materialParams.iridescence = extension.iridescenceFactor;
  
      }
  
      if ( extension.iridescenceTexture !== undefined ) {
  
        pending.push( parser.assignTexture( materialParams, 'iridescenceMap', extension.iridescenceTexture ) );
  
      }
  
      if ( extension.iridescenceIor !== undefined ) {
  
        materialParams.iridescenceIOR = extension.iridescenceIor;
  
      }
  
      if ( materialParams.iridescenceThicknessRange === undefined ) {
  
        materialParams.iridescenceThicknessRange = [ 100, 400 ];
  
      }
  
      if ( extension.iridescenceThicknessMinimum !== undefined ) {
  
        materialParams.iridescenceThicknessRange[ 0 ] = extension.iridescenceThicknessMinimum;
  
      }
  
      if ( extension.iridescenceThicknessMaximum !== undefined ) {
  
        materialParams.iridescenceThicknessRange[ 1 ] = extension.iridescenceThicknessMaximum;
  
      }
  
      if ( extension.iridescenceThicknessTexture !== undefined ) {
  
        pending.push( parser.assignTexture( materialParams, 'iridescenceThicknessMap', extension.iridescenceThicknessTexture ) );
  
      }
  
      return Promise.all( pending );
  
    }
  
  }
  
  /**
   * Sheen Materials Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Khronos/KHR_materials_sheen
   */
  class GLTFMaterialsSheenExtension {
  
    constructor( parser ) {
  
      this.parser = parser;
      this.name = EXTENSIONS.KHR_MATERIALS_SHEEN;
  
    }
  
    getMaterialType( materialIndex ) {
  
      const parser = this.parser;
      const materialDef = parser.json.materials[ materialIndex ];
  
      if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) return null;
  
      return MeshPhysicalMaterial;
  
    }
  
    extendMaterialParams( materialIndex, materialParams ) {
  
      const parser = this.parser;
      const materialDef = parser.json.materials[ materialIndex ];
  
      if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {
  
        return Promise.resolve();
  
      }
  
      const pending = [];
  
      materialParams.sheenColor = new Color( 0, 0, 0 );
      materialParams.sheenRoughness = 0;
      materialParams.sheen = 1;
  
      const extension = materialDef.extensions[ this.name ];
  
      if ( extension.sheenColorFactor !== undefined ) {
  
        const colorFactor = extension.sheenColorFactor;
        materialParams.sheenColor.setRGB( colorFactor[ 0 ], colorFactor[ 1 ], colorFactor[ 2 ], LinearSRGBColorSpace );
  
      }
  
      if ( extension.sheenRoughnessFactor !== undefined ) {
  
        materialParams.sheenRoughness = extension.sheenRoughnessFactor;
  
      }
  
      if ( extension.sheenColorTexture !== undefined ) {
  
        pending.push( parser.assignTexture( materialParams, 'sheenColorMap', extension.sheenColorTexture, SRGBColorSpace ) );
  
      }
  
      if ( extension.sheenRoughnessTexture !== undefined ) {
  
        pending.push( parser.assignTexture( materialParams, 'sheenRoughnessMap', extension.sheenRoughnessTexture ) );
  
      }
  
      return Promise.all( pending );
  
    }
  
  }
  
  /**
   * Transmission Materials Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_transmission
   * Draft: https://github.com/KhronosGroup/glTF/pull/1698
   */
  class GLTFMaterialsTransmissionExtension {
  
    constructor( parser ) {
  
      this.parser = parser;
      this.name = EXTENSIONS.KHR_MATERIALS_TRANSMISSION;
  
    }
  
    getMaterialType( materialIndex ) {
  
      const parser = this.parser;
      const materialDef = parser.json.materials[ materialIndex ];
  
      if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) return null;
  
      return MeshPhysicalMaterial;
  
    }
  
    extendMaterialParams( materialIndex, materialParams ) {
  
      const parser = this.parser;
      const materialDef = parser.json.materials[ materialIndex ];
  
      if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {
  
        return Promise.resolve();
  
      }
  
      const pending = [];
  
      const extension = materialDef.extensions[ this.name ];
  
      if ( extension.transmissionFactor !== undefined ) {
  
        materialParams.transmission = extension.transmissionFactor;
  
      }
  
      if ( extension.transmissionTexture !== undefined ) {
  
        pending.push( parser.assignTexture( materialParams, 'transmissionMap', extension.transmissionTexture ) );
  
      }
  
      return Promise.all( pending );
  
    }
  
  }
  
  /**
   * Materials Volume Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_volume
   */
  class GLTFMaterialsVolumeExtension {
  
    constructor( parser ) {
  
      this.parser = parser;
      this.name = EXTENSIONS.KHR_MATERIALS_VOLUME;
  
    }
  
    getMaterialType( materialIndex ) {
  
      const parser = this.parser;
      const materialDef = parser.json.materials[ materialIndex ];
  
      if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) return null;
  
      return MeshPhysicalMaterial;
  
    }
  
    extendMaterialParams( materialIndex, materialParams ) {
  
      const parser = this.parser;
      const materialDef = parser.json.materials[ materialIndex ];
  
      if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {
  
        return Promise.resolve();
  
      }
  
      const pending = [];
  
      const extension = materialDef.extensions[ this.name ];
  
      materialParams.thickness = extension.thicknessFactor !== undefined ? extension.thicknessFactor : 0;
  
      if ( extension.thicknessTexture !== undefined ) {
  
        pending.push( parser.assignTexture( materialParams, 'thicknessMap', extension.thicknessTexture ) );
  
      }
  
      materialParams.attenuationDistance = extension.attenuationDistance || Infinity;
  
      const colorArray = extension.attenuationColor || [ 1, 1, 1 ];
      materialParams.attenuationColor = new Color().setRGB( colorArray[ 0 ], colorArray[ 1 ], colorArray[ 2 ], LinearSRGBColorSpace );
  
      return Promise.all( pending );
  
    }
  
  }
  
  /**
   * Materials ior Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_ior
   */
  class GLTFMaterialsIorExtension {
  
    constructor( parser ) {
  
      this.parser = parser;
      this.name = EXTENSIONS.KHR_MATERIALS_IOR;
  
    }
  
    getMaterialType( materialIndex ) {
  
      const parser = this.parser;
      const materialDef = parser.json.materials[ materialIndex ];
  
      if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) return null;
  
      return MeshPhysicalMaterial;
  
    }
  
    extendMaterialParams( materialIndex, materialParams ) {
  
      const parser = this.parser;
      const materialDef = parser.json.materials[ materialIndex ];
  
      if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {
  
        return Promise.resolve();
  
      }
  
      const extension = materialDef.extensions[ this.name ];
  
      materialParams.ior = extension.ior !== undefined ? extension.ior : 1.5;
  
      return Promise.resolve();
  
    }
  
  }
  
  /**
   * Materials specular Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_specular
   */
  class GLTFMaterialsSpecularExtension {
  
    constructor( parser ) {
  
      this.parser = parser;
      this.name = EXTENSIONS.KHR_MATERIALS_SPECULAR;
  
    }
  
    getMaterialType( materialIndex ) {
  
      const parser = this.parser;
      const materialDef = parser.json.materials[ materialIndex ];
  
      if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) return null;
  
      return MeshPhysicalMaterial;
  
    }
  
    extendMaterialParams( materialIndex, materialParams ) {
  
      const parser = this.parser;
      const materialDef = parser.json.materials[ materialIndex ];
  
      if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {
  
        return Promise.resolve();
  
      }
  
      const pending = [];
  
      const extension = materialDef.extensions[ this.name ];
  
      materialParams.specularIntensity = extension.specularFactor !== undefined ? extension.specularFactor : 1.0;
  
      if ( extension.specularTexture !== undefined ) {
  
        pending.push( parser.assignTexture( materialParams, 'specularIntensityMap', extension.specularTexture ) );
  
      }
  
      const colorArray = extension.specularColorFactor || [ 1, 1, 1 ];
      materialParams.specularColor = new Color().setRGB( colorArray[ 0 ], colorArray[ 1 ], colorArray[ 2 ], LinearSRGBColorSpace );
  
      if ( extension.specularColorTexture !== undefined ) {
  
        pending.push( parser.assignTexture( materialParams, 'specularColorMap', extension.specularColorTexture, SRGBColorSpace ) );
  
      }
  
      return Promise.all( pending );
  
    }
  
  }
  
  /**
   * Materials anisotropy Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_anisotropy
   */
  class GLTFMaterialsAnisotropyExtension {
  
    constructor( parser ) {
  
      this.parser = parser;
      this.name = EXTENSIONS.KHR_MATERIALS_ANISOTROPY;
  
    }
  
    getMaterialType( materialIndex ) {
  
      const parser = this.parser;
      const materialDef = parser.json.materials[ materialIndex ];
  
      if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) return null;
  
      return MeshPhysicalMaterial;
  
    }
  
    extendMaterialParams( materialIndex, materialParams ) {
  
      const parser = this.parser;
      const materialDef = parser.json.materials[ materialIndex ];
  
      if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {
  
        return Promise.resolve();
  
      }
  
      const pending = [];
  
      const extension = materialDef.extensions[ this.name ];
  
      if ( extension.anisotropyStrength !== undefined ) {
  
        materialParams.anisotropy = extension.anisotropyStrength;
  
      }
  
      if ( extension.anisotropyRotation !== undefined ) {
  
        materialParams.anisotropyRotation = extension.anisotropyRotation;
  
      }
  
      if ( extension.anisotropyTexture !== undefined ) {
  
        pending.push( parser.assignTexture( materialParams, 'anisotropyMap', extension.anisotropyTexture ) );
  
      }
  
      return Promise.all( pending );
  
    }
  
  }
  
  /**
   * BasisU Texture Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_texture_basisu
   */
  class GLTFTextureBasisUExtension {
  
    constructor( parser ) {
  
      this.parser = parser;
      this.name = EXTENSIONS.KHR_TEXTURE_BASISU;
  
    }
  
    loadTexture( textureIndex ) {
  
      const parser = this.parser;
      const json = parser.json;
  
      const textureDef = json.textures[ textureIndex ];
  
      if ( ! textureDef.extensions || ! textureDef.extensions[ this.name ] ) {
  
        return null;
  
      }
  
      const extension = textureDef.extensions[ this.name ];
      const loader = parser.options.ktx2Loader;
  
      if ( ! loader ) {
  
        if ( json.extensionsRequired && json.extensionsRequired.indexOf( this.name ) >= 0 ) {
  
          throw new Error( 'THREE.GLTFLoader: setKTX2Loader must be called before loading KTX2 textures' );
  
        } else {
  
          // Assumes that the extension is optional and that a fallback texture is present
          return null;
  
        }
  
      }
  
      return parser.loadTextureImage( textureIndex, extension.source, loader );
  
    }
  
  }
  
  /**
   * WebP Texture Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/EXT_texture_webp
   */
  class GLTFTextureWebPExtension {
  
    constructor( parser ) {
  
      this.parser = parser;
      this.name = EXTENSIONS.EXT_TEXTURE_WEBP;
      this.isSupported = null;
  
    }
  
    loadTexture( textureIndex ) {
  
      const name = this.name;
      const parser = this.parser;
      const json = parser.json;
  
      const textureDef = json.textures[ textureIndex ];
  
      if ( ! textureDef.extensions || ! textureDef.extensions[ name ] ) {
  
        return null;
  
      }
  
      const extension = textureDef.extensions[ name ];
      const source = json.images[ extension.source ];
  
      let loader = parser.textureLoader;
      if ( source.uri ) {
  
        const handler = parser.options.manager.getHandler( source.uri );
        if ( handler !== null ) loader = handler;
  
      }
  
      return this.detectSupport().then( function ( isSupported ) {
  
        if ( isSupported ) return parser.loadTextureImage( textureIndex, extension.source, loader );
  
        if ( json.extensionsRequired && json.extensionsRequired.indexOf( name ) >= 0 ) {
  
          throw new Error( 'THREE.GLTFLoader: WebP required by asset but unsupported.' );
  
        }
  
        // Fall back to PNG or JPEG.
        return parser.loadTexture( textureIndex );
  
      } );
  
    }
  
    detectSupport() {
  
      if ( ! this.isSupported ) {
  
        this.isSupported = new Promise( function ( resolve ) {
  
          const image = new Image();
  
          // Lossy test image. Support for lossy images doesn't guarantee support for all
          // WebP images, unfortunately.
          image.src = '';
  
          image.onload = image.onerror = function () {
  
            resolve( image.height === 1 );
  
          };
  
        } );
  
      }
  
      return this.isSupported;
  
    }
  
  }
  
  /**
   * AVIF Texture Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/EXT_texture_avif
   */
  class GLTFTextureAVIFExtension {
  
    constructor( parser ) {
  
      this.parser = parser;
      this.name = EXTENSIONS.EXT_TEXTURE_AVIF;
      this.isSupported = null;
  
    }
  
    loadTexture( textureIndex ) {
  
      const name = this.name;
      const parser = this.parser;
      const json = parser.json;
  
      const textureDef = json.textures[ textureIndex ];
  
      if ( ! textureDef.extensions || ! textureDef.extensions[ name ] ) {
  
        return null;
  
      }
  
      const extension = textureDef.extensions[ name ];
      const source = json.images[ extension.source ];
  
      let loader = parser.textureLoader;
      if ( source.uri ) {
  
        const handler = parser.options.manager.getHandler( source.uri );
        if ( handler !== null ) loader = handler;
  
      }
  
      return this.detectSupport().then( function ( isSupported ) {
  
        if ( isSupported ) return parser.loadTextureImage( textureIndex, extension.source, loader );
  
        if ( json.extensionsRequired && json.extensionsRequired.indexOf( name ) >= 0 ) {
  
          throw new Error( 'THREE.GLTFLoader: AVIF required by asset but unsupported.' );
  
        }
  
        // Fall back to PNG or JPEG.
        return parser.loadTexture( textureIndex );
  
      } );
  
    }
  
    detectSupport() {
  
      if ( ! this.isSupported ) {
  
        this.isSupported = new Promise( function ( resolve ) {
  
          const image = new Image();
  
          // Lossy test image.
          image.src = '';
          image.onload = image.onerror = function () {
  
            resolve( image.height === 1 );
  
          };
  
        } );
  
      }
  
      return this.isSupported;
  
    }
  
  }
  
  /**
   * meshopt BufferView Compression Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/EXT_meshopt_compression
   */
  class GLTFMeshoptCompression {
  
    constructor( parser ) {
  
      this.name = EXTENSIONS.EXT_MESHOPT_COMPRESSION;
      this.parser = parser;
  
    }
  
    loadBufferView( index ) {
  
      const json = this.parser.json;
      const bufferView = json.bufferViews[ index ];
  
      if ( bufferView.extensions && bufferView.extensions[ this.name ] ) {
  
        const extensionDef = bufferView.extensions[ this.name ];
  
        const buffer = this.parser.getDependency( 'buffer', extensionDef.buffer );
        const decoder = this.parser.options.meshoptDecoder;
  
        if ( ! decoder || ! decoder.supported ) {
  
          if ( json.extensionsRequired && json.extensionsRequired.indexOf( this.name ) >= 0 ) {
  
            throw new Error( 'THREE.GLTFLoader: setMeshoptDecoder must be called before loading compressed files' );
  
          } else {
  
            // Assumes that the extension is optional and that fallback buffer data is present
            return null;
  
          }
  
        }
  
        return buffer.then( function ( res ) {
  
          const byteOffset = extensionDef.byteOffset || 0;
          const byteLength = extensionDef.byteLength || 0;
  
          const count = extensionDef.count;
          const stride = extensionDef.byteStride;
  
          const source = new Uint8Array( res, byteOffset, byteLength );
  
          if ( decoder.decodeGltfBufferAsync ) {
  
            return decoder.decodeGltfBufferAsync( count, stride, source, extensionDef.mode, extensionDef.filter ).then( function ( res ) {
  
              return res.buffer;
  
            } );
  
          } else {
  
            // Support for MeshoptDecoder 0.18 or earlier, without decodeGltfBufferAsync
            return decoder.ready.then( function () {
  
              const result = new ArrayBuffer( count * stride );
              decoder.decodeGltfBuffer( new Uint8Array( result ), count, stride, source, extensionDef.mode, extensionDef.filter );
              return result;
  
            } );
  
          }
  
        } );
  
      } else {
  
        return null;
  
      }
  
    }
  
  }
  
  /**
   * GPU Instancing Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/EXT_mesh_gpu_instancing
   *
   */
  class GLTFMeshGpuInstancing {
  
    constructor( parser ) {
  
      this.name = EXTENSIONS.EXT_MESH_GPU_INSTANCING;
      this.parser = parser;
  
    }
  
    createNodeMesh( nodeIndex ) {
  
      const json = this.parser.json;
      const nodeDef = json.nodes[ nodeIndex ];
  
      if ( ! nodeDef.extensions || ! nodeDef.extensions[ this.name ] ||
        nodeDef.mesh === undefined ) {
  
        return null;
  
      }
  
      const meshDef = json.meshes[ nodeDef.mesh ];
  
      // No Points or Lines + Instancing support yet
  
      for ( const primitive of meshDef.primitives ) {
  
        if ( primitive.mode !== WEBGL_CONSTANTS.TRIANGLES &&
           primitive.mode !== WEBGL_CONSTANTS.TRIANGLE_STRIP &&
           primitive.mode !== WEBGL_CONSTANTS.TRIANGLE_FAN &&
           primitive.mode !== undefined ) {
  
          return null;
  
        }
  
      }
  
      const extensionDef = nodeDef.extensions[ this.name ];
      const attributesDef = extensionDef.attributes;
  
      // @TODO: Can we support InstancedMesh + SkinnedMesh?
  
      const pending = [];
      const attributes = {};
  
      for ( const key in attributesDef ) {
  
        pending.push( this.parser.getDependency( 'accessor', attributesDef[ key ] ).then( accessor => {
  
          attributes[ key ] = accessor;
          return attributes[ key ];
  
        } ) );
  
      }
  
      if ( pending.length < 1 ) {
  
        return null;
  
      }
  
      pending.push( this.parser.createNodeMesh( nodeIndex ) );
  
      return Promise.all( pending ).then( results => {
  
        const nodeObject = results.pop();
        const meshes = nodeObject.isGroup ? nodeObject.children : [ nodeObject ];
        const count = results[ 0 ].count; // All attribute counts should be same
        const instancedMeshes = [];
  
        for ( const mesh of meshes ) {
  
          // Temporal variables
          const m = new Matrix4();
          const p = new Vector3();
          const q = new Quaternion();
          const s = new Vector3( 1, 1, 1 );
  
          const instancedMesh = new InstancedMesh( mesh.geometry, mesh.material, count );
  
          for ( let i = 0; i < count; i ++ ) {
  
            if ( attributes.TRANSLATION ) {
  
              p.fromBufferAttribute( attributes.TRANSLATION, i );
  
            }
  
            if ( attributes.ROTATION ) {
  
              q.fromBufferAttribute( attributes.ROTATION, i );
  
            }
  
            if ( attributes.SCALE ) {
  
              s.fromBufferAttribute( attributes.SCALE, i );
  
            }
  
            instancedMesh.setMatrixAt( i, m.compose( p, q, s ) );
  
          }
  
          // Add instance attributes to the geometry, excluding TRS.
          for ( const attributeName in attributes ) {
  
            if ( attributeName === '_COLOR_0' ) {
  
              const attr = attributes[ attributeName ];
              instancedMesh.instanceColor = new InstancedBufferAttribute( attr.array, attr.itemSize, attr.normalized );
  
            } else if ( attributeName !== 'TRANSLATION' &&
               attributeName !== 'ROTATION' &&
               attributeName !== 'SCALE' ) {
  
              mesh.geometry.setAttribute( attributeName, attributes[ attributeName ] );
  
            }
  
          }
  
          // Just in case
          Object3D.prototype.copy.call( instancedMesh, mesh );
  
          this.parser.assignFinalMaterial( instancedMesh );
  
          instancedMeshes.push( instancedMesh );
  
        }
  
        if ( nodeObject.isGroup ) {
  
          nodeObject.clear();
  
          nodeObject.add( ... instancedMeshes );
  
          return nodeObject;
  
        }
  
        return instancedMeshes[ 0 ];
  
      } );
  
    }
  
  }
  
  /* BINARY EXTENSION */
  const BINARY_EXTENSION_HEADER_MAGIC = 'glTF';
  const BINARY_EXTENSION_HEADER_LENGTH = 12;
  const BINARY_EXTENSION_CHUNK_TYPES = { JSON: 0x4E4F534A, BIN: 0x004E4942 };
  
  class GLTFBinaryExtension {
  
    constructor( data ) {
  
      this.name = EXTENSIONS.KHR_BINARY_GLTF;
      this.content = null;
      this.body = null;
  
      const headerView = new DataView( data, 0, BINARY_EXTENSION_HEADER_LENGTH );
      const textDecoder = new TextDecoder();
  
      this.header = {
        magic: textDecoder.decode( new Uint8Array( data.slice( 0, 4 ) ) ),
        version: headerView.getUint32( 4, true ),
        length: headerView.getUint32( 8, true )
      };
  
      if ( this.header.magic !== BINARY_EXTENSION_HEADER_MAGIC ) {
  
        throw new Error( 'THREE.GLTFLoader: Unsupported glTF-Binary header.' );
  
      } else if ( this.header.version < 2.0 ) {
  
        throw new Error( 'THREE.GLTFLoader: Legacy binary file detected.' );
  
      }
  
      const chunkContentsLength = this.header.length - BINARY_EXTENSION_HEADER_LENGTH;
      const chunkView = new DataView( data, BINARY_EXTENSION_HEADER_LENGTH );
      let chunkIndex = 0;
  
      while ( chunkIndex < chunkContentsLength ) {
  
        const chunkLength = chunkView.getUint32( chunkIndex, true );
        chunkIndex += 4;
  
        const chunkType = chunkView.getUint32( chunkIndex, true );
        chunkIndex += 4;
  
        if ( chunkType === BINARY_EXTENSION_CHUNK_TYPES.JSON ) {
  
          const contentArray = new Uint8Array( data, BINARY_EXTENSION_HEADER_LENGTH + chunkIndex, chunkLength );
          this.content = textDecoder.decode( contentArray );
  
        } else if ( chunkType === BINARY_EXTENSION_CHUNK_TYPES.BIN ) {
  
          const byteOffset = BINARY_EXTENSION_HEADER_LENGTH + chunkIndex;
          this.body = data.slice( byteOffset, byteOffset + chunkLength );
  
        }
  
        // Clients must ignore chunks with unknown types.
  
        chunkIndex += chunkLength;
  
      }
  
      if ( this.content === null ) {
  
        throw new Error( 'THREE.GLTFLoader: JSON content not found.' );
  
      }
  
    }
  
  }
  
  /**
   * DRACO Mesh Compression Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_draco_mesh_compression
   */
  class GLTFDracoMeshCompressionExtension {
  
    constructor( json, dracoLoader ) {
  
      if ( ! dracoLoader ) {
  
        throw new Error( 'THREE.GLTFLoader: No DRACOLoader instance provided.' );
  
      }
  
      this.name = EXTENSIONS.KHR_DRACO_MESH_COMPRESSION;
      this.json = json;
      this.dracoLoader = dracoLoader;
      this.dracoLoader.preload();
  
    }
  
    decodePrimitive( primitive, parser ) {
  
      const json = this.json;
      const dracoLoader = this.dracoLoader;
      const bufferViewIndex = primitive.extensions[ this.name ].bufferView;
      const gltfAttributeMap = primitive.extensions[ this.name ].attributes;
      const threeAttributeMap = {};
      const attributeNormalizedMap = {};
      const attributeTypeMap = {};
  
      for ( const attributeName in gltfAttributeMap ) {
  
        const threeAttributeName = ATTRIBUTES[ attributeName ] || attributeName.toLowerCase();
  
        threeAttributeMap[ threeAttributeName ] = gltfAttributeMap[ attributeName ];
  
      }
  
      for ( const attributeName in primitive.attributes ) {
  
        const threeAttributeName = ATTRIBUTES[ attributeName ] || attributeName.toLowerCase();
  
        if ( gltfAttributeMap[ attributeName ] !== undefined ) {
  
          const accessorDef = json.accessors[ primitive.attributes[ attributeName ] ];
          const componentType = WEBGL_COMPONENT_TYPES[ accessorDef.componentType ];
  
          attributeTypeMap[ threeAttributeName ] = componentType.name;
          attributeNormalizedMap[ threeAttributeName ] = accessorDef.normalized === true;
  
        }
  
      }
  
      return parser.getDependency( 'bufferView', bufferViewIndex ).then( function ( bufferView ) {
  
        return new Promise( function ( resolve ) {
  
          dracoLoader.decodeDracoFile( bufferView, function ( geometry ) {
  
            for ( const attributeName in geometry.attributes ) {
  
              const attribute = geometry.attributes[ attributeName ];
              const normalized = attributeNormalizedMap[ attributeName ];
  
              if ( normalized !== undefined ) attribute.normalized = normalized;
  
            }
  
            resolve( geometry );
  
          }, threeAttributeMap, attributeTypeMap );
  
        } );
  
      } );
  
    }
  
  }
  
  /**
   * Texture Transform Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_texture_transform
   */
  class GLTFTextureTransformExtension {
  
    constructor() {
  
      this.name = EXTENSIONS.KHR_TEXTURE_TRANSFORM;
  
    }
  
    extendTexture( texture, transform ) {
  
      if ( ( transform.texCoord === undefined || transform.texCoord === texture.channel )
        && transform.offset === undefined
        && transform.rotation === undefined
        && transform.scale === undefined ) {
  
        // See https://github.com/mrdoob/three.js/issues/21819.
        return texture;
  
      }
  
      texture = texture.clone();
  
      if ( transform.texCoord !== undefined ) {
  
        texture.channel = transform.texCoord;
  
      }
  
      if ( transform.offset !== undefined ) {
  
        texture.offset.fromArray( transform.offset );
  
      }
  
      if ( transform.rotation !== undefined ) {
  
        texture.rotation = transform.rotation;
  
      }
  
      if ( transform.scale !== undefined ) {
  
        texture.repeat.fromArray( transform.scale );
  
      }
  
      texture.needsUpdate = true;
  
      return texture;
  
    }
  
  }
  
  /**
   * Mesh Quantization Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_mesh_quantization
   */
  class GLTFMeshQuantizationExtension {
  
    constructor() {
  
      this.name = EXTENSIONS.KHR_MESH_QUANTIZATION;
  
    }
  
  }
  
  /*********************************/
  /********** INTERPOLATION ********/
  /*********************************/
  
  // Spline Interpolation
  // Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#appendix-c-spline-interpolation
  class GLTFCubicSplineInterpolant extends Interpolant {
  
    constructor( parameterPositions, sampleValues, sampleSize, resultBuffer ) {
  
      super( parameterPositions, sampleValues, sampleSize, resultBuffer );
  
    }
  
    copySampleValue_( index ) {
  
      // Copies a sample value to the result buffer. See description of glTF
      // CUBICSPLINE values layout in interpolate_() function below.
  
      const result = this.resultBuffer,
        values = this.sampleValues,
        valueSize = this.valueSize,
        offset = index * valueSize * 3 + valueSize;
  
      for ( let i = 0; i !== valueSize; i ++ ) {
  
        result[ i ] = values[ offset + i ];
  
      }
  
      return result;
  
    }
  
    interpolate_( i1, t0, t, t1 ) {
  
      const result = this.resultBuffer;
      const values = this.sampleValues;
      const stride = this.valueSize;
  
      const stride2 = stride * 2;
      const stride3 = stride * 3;
  
      const td = t1 - t0;
  
      const p = ( t - t0 ) / td;
      const pp = p * p;
      const ppp = pp * p;
  
      const offset1 = i1 * stride3;
      const offset0 = offset1 - stride3;
  
      const s2 = - 2 * ppp + 3 * pp;
      const s3 = ppp - pp;
      const s0 = 1 - s2;
      const s1 = s3 - pp + p;
  
      // Layout of keyframe output values for CUBICSPLINE animations:
      //   [ inTangent_1, splineVertex_1, outTangent_1, inTangent_2, splineVertex_2, ... ]
      for ( let i = 0; i !== stride; i ++ ) {
  
        const p0 = values[ offset0 + i + stride ]; // splineVertex_k
        const m0 = values[ offset0 + i + stride2 ] * td; // outTangent_k * (t_k+1 - t_k)
        const p1 = values[ offset1 + i + stride ]; // splineVertex_k+1
        const m1 = values[ offset1 + i ] * td; // inTangent_k+1 * (t_k+1 - t_k)
  
        result[ i ] = s0 * p0 + s1 * m0 + s2 * p1 + s3 * m1;
  
      }
  
      return result;
  
    }
  
  }
  
  const _q = new Quaternion();
  
  class GLTFCubicSplineQuaternionInterpolant extends GLTFCubicSplineInterpolant {
  
    interpolate_( i1, t0, t, t1 ) {
  
      const result = super.interpolate_( i1, t0, t, t1 );
  
      _q.fromArray( result ).normalize().toArray( result );
  
      return result;
  
    }
  
  }
  
  
  /*********************************/
  /********** INTERNALS ************/
  /*********************************/
  
  /* CONSTANTS */
  
  const WEBGL_CONSTANTS = {
    FLOAT: 5126,
    //FLOAT_MAT2: 35674,
    FLOAT_MAT3: 35675,
    FLOAT_MAT4: 35676,
    FLOAT_VEC2: 35664,
    FLOAT_VEC3: 35665,
    FLOAT_VEC4: 35666,
    LINEAR: 9729,
    REPEAT: 10497,
    SAMPLER_2D: 35678,
    POINTS: 0,
    LINES: 1,
    LINE_LOOP: 2,
    LINE_STRIP: 3,
    TRIANGLES: 4,
    TRIANGLE_STRIP: 5,
    TRIANGLE_FAN: 6,
    UNSIGNED_BYTE: 5121,
    UNSIGNED_SHORT: 5123
  };
  
  const WEBGL_COMPONENT_TYPES = {
    5120: Int8Array,
    5121: Uint8Array,
    5122: Int16Array,
    5123: Uint16Array,
    5125: Uint32Array,
    5126: Float32Array
  };
  
  const WEBGL_FILTERS = {
    9728: NearestFilter,
    9729: LinearFilter,
    9984: NearestMipmapNearestFilter,
    9985: LinearMipmapNearestFilter,
    9986: NearestMipmapLinearFilter,
    9987: LinearMipmapLinearFilter
  };
  
  const WEBGL_WRAPPINGS = {
    33071: ClampToEdgeWrapping,
    33648: MirroredRepeatWrapping,
    10497: RepeatWrapping
  };
  
  const WEBGL_TYPE_SIZES = {
    'SCALAR': 1,
    'VEC2': 2,
    'VEC3': 3,
    'VEC4': 4,
    'MAT2': 4,
    'MAT3': 9,
    'MAT4': 16
  };
  
  const ATTRIBUTES = {
    POSITION: 'position',
    NORMAL: 'normal',
    TANGENT: 'tangent',
    TEXCOORD_0: 'uv',
    TEXCOORD_1: 'uv1',
    TEXCOORD_2: 'uv2',
    TEXCOORD_3: 'uv3',
    COLOR_0: 'color',
    WEIGHTS_0: 'skinWeight',
    JOINTS_0: 'skinIndex',
  };
  
  const PATH_PROPERTIES = {
    scale: 'scale',
    translation: 'position',
    rotation: 'quaternion',
    weights: 'morphTargetInfluences'
  };
  
  const INTERPOLATION = {
    CUBICSPLINE: undefined, // We use a custom interpolant (GLTFCubicSplineInterpolation) for CUBICSPLINE tracks. Each
                              // keyframe track will be initialized with a default interpolation type, then modified.
    LINEAR: InterpolateLinear,
    STEP: InterpolateDiscrete
  };
  
  const ALPHA_MODES = {
    OPAQUE: 'OPAQUE',
    MASK: 'MASK',
    BLEND: 'BLEND'
  };
  
  /**
   * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#default-material
   */
  function createDefaultMaterial( cache ) {
  
    if ( cache[ 'DefaultMaterial' ] === undefined ) {
  
      cache[ 'DefaultMaterial' ] = new MeshStandardMaterial( {
        color: 0xFFFFFF,
        emissive: 0x000000,
        metalness: 1,
        roughness: 1,
        transparent: false,
        depthTest: true,
        side: FrontSide
      } );
  
    }
  
    return cache[ 'DefaultMaterial' ];
  
  }
  
  function addUnknownExtensionsToUserData( knownExtensions, object, objectDef ) {
  
    // Add unknown glTF extensions to an object's userData.
  
    for ( const name in objectDef.extensions ) {
  
      if ( knownExtensions[ name ] === undefined ) {
  
        object.userData.gltfExtensions = object.userData.gltfExtensions || {};
        object.userData.gltfExtensions[ name ] = objectDef.extensions[ name ];
  
      }
  
    }
  
  }
  
  /**
   * @param {Object3D|Material|BufferGeometry} object
   * @param {GLTF.definition} gltfDef
   */
  function assignExtrasToUserData( object, gltfDef ) {
  
    if ( gltfDef.extras !== undefined ) {
  
      if ( typeof gltfDef.extras === 'object' ) {
  
        Object.assign( object.userData, gltfDef.extras );
  
      } else {
  
        console.warn( 'THREE.GLTFLoader: Ignoring primitive type .extras, ' + gltfDef.extras );
  
      }
  
    }
  
  }
  
  /**
   * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#morph-targets
   *
   * @param {BufferGeometry} geometry
   * @param {Array<GLTF.Target>} targets
   * @param {GLTFParser} parser
   * @return {Promise<BufferGeometry>}
   */
  function addMorphTargets( geometry, targets, parser ) {
  
    let hasMorphPosition = false;
    let hasMorphNormal = false;
    let hasMorphColor = false;
  
    for ( let i = 0, il = targets.length; i < il; i ++ ) {
  
      const target = targets[ i ];
  
      if ( target.POSITION !== undefined ) hasMorphPosition = true;
      if ( target.NORMAL !== undefined ) hasMorphNormal = true;
      if ( target.COLOR_0 !== undefined ) hasMorphColor = true;
  
      if ( hasMorphPosition && hasMorphNormal && hasMorphColor ) break;
  
    }
  
    if ( ! hasMorphPosition && ! hasMorphNormal && ! hasMorphColor ) return Promise.resolve( geometry );
  
    const pendingPositionAccessors = [];
    const pendingNormalAccessors = [];
    const pendingColorAccessors = [];
  
    for ( let i = 0, il = targets.length; i < il; i ++ ) {
  
      const target = targets[ i ];
  
      if ( hasMorphPosition ) {
  
        const pendingAccessor = target.POSITION !== undefined
          ? parser.getDependency( 'accessor', target.POSITION )
          : geometry.attributes.position;
  
        pendingPositionAccessors.push( pendingAccessor );
  
      }
  
      if ( hasMorphNormal ) {
  
        const pendingAccessor = target.NORMAL !== undefined
          ? parser.getDependency( 'accessor', target.NORMAL )
          : geometry.attributes.normal;
  
        pendingNormalAccessors.push( pendingAccessor );
  
      }
  
      if ( hasMorphColor ) {
  
        const pendingAccessor = target.COLOR_0 !== undefined
          ? parser.getDependency( 'accessor', target.COLOR_0 )
          : geometry.attributes.color;
  
        pendingColorAccessors.push( pendingAccessor );
  
      }
  
    }
  
    return Promise.all( [
      Promise.all( pendingPositionAccessors ),
      Promise.all( pendingNormalAccessors ),
      Promise.all( pendingColorAccessors )
    ] ).then( function ( accessors ) {
  
      const morphPositions = accessors[ 0 ];
      const morphNormals = accessors[ 1 ];
      const morphColors = accessors[ 2 ];
  
      if ( hasMorphPosition ) geometry.morphAttributes.position = morphPositions;
      if ( hasMorphNormal ) geometry.morphAttributes.normal = morphNormals;
      if ( hasMorphColor ) geometry.morphAttributes.color = morphColors;
      geometry.morphTargetsRelative = true;
  
      return geometry;
  
    } );
  
  }
  
  /**
   * @param {Mesh} mesh
   * @param {GLTF.Mesh} meshDef
   */
  function updateMorphTargets( mesh, meshDef ) {
  
    mesh.updateMorphTargets();
  
    if ( meshDef.weights !== undefined ) {
  
      for ( let i = 0, il = meshDef.weights.length; i < il; i ++ ) {
  
        mesh.morphTargetInfluences[ i ] = meshDef.weights[ i ];
  
      }
  
    }
  
    // .extras has user-defined data, so check that .extras.targetNames is an array.
    if ( meshDef.extras && Array.isArray( meshDef.extras.targetNames ) ) {
  
      const targetNames = meshDef.extras.targetNames;
  
      if ( mesh.morphTargetInfluences.length === targetNames.length ) {
  
        mesh.morphTargetDictionary = {};
  
        for ( let i = 0, il = targetNames.length; i < il; i ++ ) {
  
          mesh.morphTargetDictionary[ targetNames[ i ] ] = i;
  
        }
  
      } else {
  
        console.warn( 'THREE.GLTFLoader: Invalid extras.targetNames length. Ignoring names.' );
  
      }
  
    }
  
  }
  
  function createPrimitiveKey( primitiveDef ) {
  
    let geometryKey;
  
    const dracoExtension = primitiveDef.extensions && primitiveDef.extensions[ EXTENSIONS.KHR_DRACO_MESH_COMPRESSION ];
  
    if ( dracoExtension ) {
  
      geometryKey = 'draco:' + dracoExtension.bufferView
          + ':' + dracoExtension.indices
          + ':' + createAttributesKey( dracoExtension.attributes );
  
    } else {
  
      geometryKey = primitiveDef.indices + ':' + createAttributesKey( primitiveDef.attributes ) + ':' + primitiveDef.mode;
  
    }
  
    if ( primitiveDef.targets !== undefined ) {
  
      for ( let i = 0, il = primitiveDef.targets.length; i < il; i ++ ) {
  
        geometryKey += ':' + createAttributesKey( primitiveDef.targets[ i ] );
  
      }
  
    }
  
    return geometryKey;
  
  }
  
  function createAttributesKey( attributes ) {
  
    let attributesKey = '';
  
    const keys = Object.keys( attributes ).sort();
  
    for ( let i = 0, il = keys.length; i < il; i ++ ) {
  
      attributesKey += keys[ i ] + ':' + attributes[ keys[ i ] ] + ';';
  
    }
  
    return attributesKey;
  
  }
  
  function getNormalizedComponentScale( constructor ) {
  
    // Reference:
    // https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_mesh_quantization#encoding-quantized-data
  
    switch ( constructor ) {
  
      case Int8Array:
        return 1 / 127;
  
      case Uint8Array:
        return 1 / 255;
  
      case Int16Array:
        return 1 / 32767;
  
      case Uint16Array:
        return 1 / 65535;
  
      default:
        throw new Error( 'THREE.GLTFLoader: Unsupported normalized accessor component type.' );
  
    }
  
  }
  
  function getImageURIMimeType( uri ) {
  
    if ( uri.search( /\.jpe?g($|\?)/i ) > 0 || uri.search( /^data\:image\/jpeg/ ) === 0 ) return 'image/jpeg';
    if ( uri.search( /\.webp($|\?)/i ) > 0 || uri.search( /^data\:image\/webp/ ) === 0 ) return 'image/webp';
  
    return 'image/png';
  
  }
  
  const _identityMatrix = new Matrix4();
  
  /* GLTF PARSER */
  
  class GLTFParser {
  
    constructor( json = {}, options = {} ) {
  
      this.json = json;
      this.extensions = {};
      this.plugins = {};
      this.options = options;
  
      // loader object cache
      this.cache = new GLTFRegistry();
  
      // associations between Three.js objects and glTF elements
      this.associations = new Map();
  
      // BufferGeometry caching
      this.primitiveCache = {};
  
      // Node cache
      this.nodeCache = {};
  
      // Object3D instance caches
      this.meshCache = { refs: {}, uses: {} };
      this.cameraCache = { refs: {}, uses: {} };
      this.lightCache = { refs: {}, uses: {} };
  
      this.sourceCache = {};
      this.textureCache = {};
  
      // Track node names, to ensure no duplicates
      this.nodeNamesUsed = {};
  
      // Use an ImageBitmapLoader if imageBitmaps are supported. Moves much of the
      // expensive work of uploading a texture to the GPU off the main thread.
  
      let isSafari = false;
      let isFirefox = false;
      let firefoxVersion = - 1;
  
      if ( typeof navigator !== 'undefined' ) {
  
        isSafari = /^((?!chrome|android).)*safari/i.test( navigator.userAgent ) === true;
        isFirefox = navigator.userAgent.indexOf( 'Firefox' ) > - 1;
        firefoxVersion = isFirefox ? navigator.userAgent.match( /Firefox\/([0-9]+)\./ )[ 1 ] : - 1;
  
      }
  
      if ( typeof createImageBitmap === 'undefined' || isSafari || ( isFirefox && firefoxVersion < 98 ) ) {
  
        this.textureLoader = new TextureLoader( this.options.manager );
  
      } else {
  
        this.textureLoader = new ImageBitmapLoader( this.options.manager );
  
      }
  
      this.textureLoader.setCrossOrigin( this.options.crossOrigin );
      this.textureLoader.setRequestHeader( this.options.requestHeader );
  
      this.fileLoader = new FileLoader( this.options.manager );
      this.fileLoader.setResponseType( 'arraybuffer' );
  
      if ( this.options.crossOrigin === 'use-credentials' ) {
  
        this.fileLoader.setWithCredentials( true );
  
      }
  
    }
  
    setExtensions( extensions ) {
  
      this.extensions = extensions;
  
    }
  
    setPlugins( plugins ) {
  
      this.plugins = plugins;
  
    }
  
    parse( onLoad, onError ) {
  
      const parser = this;
      const json = this.json;
      const extensions = this.extensions;
  
      // Clear the loader cache
      this.cache.removeAll();
      this.nodeCache = {};
  
      // Mark the special nodes/meshes in json for efficient parse
      this._invokeAll( function ( ext ) {
  
        return ext._markDefs && ext._markDefs();
  
      } );
  
      Promise.all( this._invokeAll( function ( ext ) {
  
        return ext.beforeRoot && ext.beforeRoot();
  
      } ) ).then( function () {
  
        return Promise.all( [
  
          parser.getDependencies( 'scene' ),
          parser.getDependencies( 'animation' ),
          parser.getDependencies( 'camera' ),
  
        ] );
  
      } ).then( function ( dependencies ) {
  
        const result = {
          scene: dependencies[ 0 ][ json.scene || 0 ],
          scenes: dependencies[ 0 ],
          animations: dependencies[ 1 ],
          cameras: dependencies[ 2 ],
          asset: json.asset,
          parser: parser,
          userData: {}
        };
  
        addUnknownExtensionsToUserData( extensions, result, json );
  
        assignExtrasToUserData( result, json );
  
        return Promise.all( parser._invokeAll( function ( ext ) {
  
          return ext.afterRoot && ext.afterRoot( result );
  
        } ) ).then( function () {
  
          onLoad( result );
  
        } );
  
      } ).catch( onError );
  
    }
  
    /**
     * Marks the special nodes/meshes in json for efficient parse.
     */
    _markDefs() {
  
      const nodeDefs = this.json.nodes || [];
      const skinDefs = this.json.skins || [];
      const meshDefs = this.json.meshes || [];
  
      // Nothing in the node definition indicates whether it is a Bone or an
      // Object3D. Use the skins' joint references to mark bones.
      for ( let skinIndex = 0, skinLength = skinDefs.length; skinIndex < skinLength; skinIndex ++ ) {
  
        const joints = skinDefs[ skinIndex ].joints;
  
        for ( let i = 0, il = joints.length; i < il; i ++ ) {
  
          nodeDefs[ joints[ i ] ].isBone = true;
  
        }
  
      }
  
      // Iterate over all nodes, marking references to shared resources,
      // as well as skeleton joints.
      for ( let nodeIndex = 0, nodeLength = nodeDefs.length; nodeIndex < nodeLength; nodeIndex ++ ) {
  
        const nodeDef = nodeDefs[ nodeIndex ];
  
        if ( nodeDef.mesh !== undefined ) {
  
          this._addNodeRef( this.meshCache, nodeDef.mesh );
  
          // Nothing in the mesh definition indicates whether it is
          // a SkinnedMesh or Mesh. Use the node's mesh reference
          // to mark SkinnedMesh if node has skin.
          if ( nodeDef.skin !== undefined ) {
  
            meshDefs[ nodeDef.mesh ].isSkinnedMesh = true;
  
          }
  
        }
  
        if ( nodeDef.camera !== undefined ) {
  
          this._addNodeRef( this.cameraCache, nodeDef.camera );
  
        }
  
      }
  
    }
  
    /**
     * Counts references to shared node / Object3D resources. These resources
     * can be reused, or "instantiated", at multiple nodes in the scene
     * hierarchy. Mesh, Camera, and Light instances are instantiated and must
     * be marked. Non-scenegraph resources (like Materials, Geometries, and
     * Textures) can be reused directly and are not marked here.
     *
     * Example: CesiumMilkTruck sample model reuses "Wheel" meshes.
     */
    _addNodeRef( cache, index ) {
  
      if ( index === undefined ) return;
  
      if ( cache.refs[ index ] === undefined ) {
  
        cache.refs[ index ] = cache.uses[ index ] = 0;
  
      }
  
      cache.refs[ index ] ++;
  
    }
  
    /** Returns a reference to a shared resource, cloning it if necessary. */
    _getNodeRef( cache, index, object ) {
  
      if ( cache.refs[ index ] <= 1 ) return object;
  
      const ref = object.clone();
  
      // Propagates mappings to the cloned object, prevents mappings on the
      // original object from being lost.
      const updateMappings = ( original, clone ) => {
  
        const mappings = this.associations.get( original );
        if ( mappings != null ) {
  
          this.associations.set( clone, mappings );
  
        }
  
        for ( const [ i, child ] of original.children.entries() ) {
  
          updateMappings( child, clone.children[ i ] );
  
        }
  
      };
  
      updateMappings( object, ref );
  
      ref.name += '_instance_' + ( cache.uses[ index ] ++ );
  
      return ref;
  
    }
  
    _invokeOne( func ) {
  
      const extensions = Object.values( this.plugins );
      extensions.push( this );
  
      for ( let i = 0; i < extensions.length; i ++ ) {
  
        const result = func( extensions[ i ] );
  
        if ( result ) return result;
  
      }
  
      return null;
  
    }
  
    _invokeAll( func ) {
  
      const extensions = Object.values( this.plugins );
      extensions.unshift( this );
  
      const pending = [];
  
      for ( let i = 0; i < extensions.length; i ++ ) {
  
        const result = func( extensions[ i ] );
  
        if ( result ) pending.push( result );
  
      }
  
      return pending;
  
    }
  
    /**
     * Requests the specified dependency asynchronously, with caching.
     * @param {string} type
     * @param {number} index
     * @return {Promise<Object3D|Material|THREE.Texture|AnimationClip|ArrayBuffer|Object>}
     */
    getDependency( type, index ) {
  
      const cacheKey = type + ':' + index;
      let dependency = this.cache.get( cacheKey );
  
      if ( ! dependency ) {
  
        switch ( type ) {
  
          case 'scene':
            dependency = this.loadScene( index );
            break;
  
          case 'node':
            dependency = this._invokeOne( function ( ext ) {
  
              return ext.loadNode && ext.loadNode( index );
  
            } );
            break;
  
          case 'mesh':
            dependency = this._invokeOne( function ( ext ) {
  
              return ext.loadMesh && ext.loadMesh( index );
  
            } );
            break;
  
          case 'accessor':
            dependency = this.loadAccessor( index );
            break;
  
          case 'bufferView':
            dependency = this._invokeOne( function ( ext ) {
  
              return ext.loadBufferView && ext.loadBufferView( index );
  
            } );
            break;
  
          case 'buffer':
            dependency = this.loadBuffer( index );
            break;
  
          case 'material':
            dependency = this._invokeOne( function ( ext ) {
  
              return ext.loadMaterial && ext.loadMaterial( index );
  
            } );
            break;
  
          case 'texture':
            dependency = this._invokeOne( function ( ext ) {
  
              return ext.loadTexture && ext.loadTexture( index );
  
            } );
            break;
  
          case 'skin':
            dependency = this.loadSkin( index );
            break;
  
          case 'animation':
            dependency = this._invokeOne( function ( ext ) {
  
              return ext.loadAnimation && ext.loadAnimation( index );
  
            } );
            break;
  
          case 'camera':
            dependency = this.loadCamera( index );
            break;
  
          default:
            dependency = this._invokeOne( function ( ext ) {
  
              return ext != this && ext.getDependency && ext.getDependency( type, index );
  
            } );
  
            if ( ! dependency ) {
  
              throw new Error( 'Unknown type: ' + type );
  
            }
  
            break;
  
        }
  
        this.cache.add( cacheKey, dependency );
  
      }
  
      return dependency;
  
    }
  
    /**
     * Requests all dependencies of the specified type asynchronously, with caching.
     * @param {string} type
     * @return {Promise<Array<Object>>}
     */
    getDependencies( type ) {
  
      let dependencies = this.cache.get( type );
  
      if ( ! dependencies ) {
  
        const parser = this;
        const defs = this.json[ type + ( type === 'mesh' ? 'es' : 's' ) ] || [];
  
        dependencies = Promise.all( defs.map( function ( def, index ) {
  
          return parser.getDependency( type, index );
  
        } ) );
  
        this.cache.add( type, dependencies );
  
      }
  
      return dependencies;
  
    }
  
    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
     * @param {number} bufferIndex
     * @return {Promise<ArrayBuffer>}
     */
    loadBuffer( bufferIndex ) {
  
      const bufferDef = this.json.buffers[ bufferIndex ];
      const loader = this.fileLoader;
  
      if ( bufferDef.type && bufferDef.type !== 'arraybuffer' ) {
  
        throw new Error( 'THREE.GLTFLoader: ' + bufferDef.type + ' buffer type is not supported.' );
  
      }
  
      // If present, GLB container is required to be the first buffer.
      if ( bufferDef.uri === undefined && bufferIndex === 0 ) {
  
        return Promise.resolve( this.extensions[ EXTENSIONS.KHR_BINARY_GLTF ].body );
  
      }
  
      const options = this.options;
  
      return new Promise( function ( resolve, reject ) {
  
        loader.load( LoaderUtils.resolveURL( bufferDef.uri, options.path ), resolve, undefined, function () {
  
          reject( new Error( 'THREE.GLTFLoader: Failed to load buffer "' + bufferDef.uri + '".' ) );
  
        } );
  
      } );
  
    }
  
    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
     * @param {number} bufferViewIndex
     * @return {Promise<ArrayBuffer>}
     */
    loadBufferView( bufferViewIndex ) {
  
      const bufferViewDef = this.json.bufferViews[ bufferViewIndex ];
  
      return this.getDependency( 'buffer', bufferViewDef.buffer ).then( function ( buffer ) {
  
        const byteLength = bufferViewDef.byteLength || 0;
        const byteOffset = bufferViewDef.byteOffset || 0;
        return buffer.slice( byteOffset, byteOffset + byteLength );
  
      } );
  
    }
  
    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#accessors
     * @param {number} accessorIndex
     * @return {Promise<BufferAttribute|InterleavedBufferAttribute>}
     */
    loadAccessor( accessorIndex ) {
  
      const parser = this;
      const json = this.json;
  
      const accessorDef = this.json.accessors[ accessorIndex ];
  
      if ( accessorDef.bufferView === undefined && accessorDef.sparse === undefined ) {
  
        const itemSize = WEBGL_TYPE_SIZES[ accessorDef.type ];
        const TypedArray = WEBGL_COMPONENT_TYPES[ accessorDef.componentType ];
        const normalized = accessorDef.normalized === true;
  
        const array = new TypedArray( accessorDef.count * itemSize );
        return Promise.resolve( new BufferAttribute( array, itemSize, normalized ) );
  
      }
  
      const pendingBufferViews = [];
  
      if ( accessorDef.bufferView !== undefined ) {
  
        pendingBufferViews.push( this.getDependency( 'bufferView', accessorDef.bufferView ) );
  
      } else {
  
        pendingBufferViews.push( null );
  
      }
  
      if ( accessorDef.sparse !== undefined ) {
  
        pendingBufferViews.push( this.getDependency( 'bufferView', accessorDef.sparse.indices.bufferView ) );
        pendingBufferViews.push( this.getDependency( 'bufferView', accessorDef.sparse.values.bufferView ) );
  
      }
  
      return Promise.all( pendingBufferViews ).then( function ( bufferViews ) {
  
        const bufferView = bufferViews[ 0 ];
  
        const itemSize = WEBGL_TYPE_SIZES[ accessorDef.type ];
        const TypedArray = WEBGL_COMPONENT_TYPES[ accessorDef.componentType ];
  
        // For VEC3: itemSize is 3, elementBytes is 4, itemBytes is 12.
        const elementBytes = TypedArray.BYTES_PER_ELEMENT;
        const itemBytes = elementBytes * itemSize;
        const byteOffset = accessorDef.byteOffset || 0;
        const byteStride = accessorDef.bufferView !== undefined ? json.bufferViews[ accessorDef.bufferView ].byteStride : undefined;
        const normalized = accessorDef.normalized === true;
        let array, bufferAttribute;
  
        // The buffer is not interleaved if the stride is the item size in bytes.
        if ( byteStride && byteStride !== itemBytes ) {
  
          // Each "slice" of the buffer, as defined by 'count' elements of 'byteStride' bytes, gets its own InterleavedBuffer
          // This makes sure that IBA.count reflects accessor.count properly
          const ibSlice = Math.floor( byteOffset / byteStride );
          const ibCacheKey = 'InterleavedBuffer:' + accessorDef.bufferView + ':' + accessorDef.componentType + ':' + ibSlice + ':' + accessorDef.count;
          let ib = parser.cache.get( ibCacheKey );
  
          if ( ! ib ) {
  
            array = new TypedArray( bufferView, ibSlice * byteStride, accessorDef.count * byteStride / elementBytes );
  
            // Integer parameters to IB/IBA are in array elements, not bytes.
            ib = new InterleavedBuffer( array, byteStride / elementBytes );
  
            parser.cache.add( ibCacheKey, ib );
  
          }
  
          bufferAttribute = new InterleavedBufferAttribute( ib, itemSize, ( byteOffset % byteStride ) / elementBytes, normalized );
  
        } else {
  
          if ( bufferView === null ) {
  
            array = new TypedArray( accessorDef.count * itemSize );
  
          } else {
  
            array = new TypedArray( bufferView, byteOffset, accessorDef.count * itemSize );
  
          }
  
          bufferAttribute = new BufferAttribute( array, itemSize, normalized );
  
        }
  
        // https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#sparse-accessors
        if ( accessorDef.sparse !== undefined ) {
  
          const itemSizeIndices = WEBGL_TYPE_SIZES.SCALAR;
          const TypedArrayIndices = WEBGL_COMPONENT_TYPES[ accessorDef.sparse.indices.componentType ];
  
          const byteOffsetIndices = accessorDef.sparse.indices.byteOffset || 0;
          const byteOffsetValues = accessorDef.sparse.values.byteOffset || 0;
  
          const sparseIndices = new TypedArrayIndices( bufferViews[ 1 ], byteOffsetIndices, accessorDef.sparse.count * itemSizeIndices );
          const sparseValues = new TypedArray( bufferViews[ 2 ], byteOffsetValues, accessorDef.sparse.count * itemSize );
  
          if ( bufferView !== null ) {
  
            // Avoid modifying the original ArrayBuffer, if the bufferView wasn't initialized with zeroes.
            bufferAttribute = new BufferAttribute( bufferAttribute.array.slice(), bufferAttribute.itemSize, bufferAttribute.normalized );
  
          }
  
          for ( let i = 0, il = sparseIndices.length; i < il; i ++ ) {
  
            const index = sparseIndices[ i ];
  
            bufferAttribute.setX( index, sparseValues[ i * itemSize ] );
            if ( itemSize >= 2 ) bufferAttribute.setY( index, sparseValues[ i * itemSize + 1 ] );
            if ( itemSize >= 3 ) bufferAttribute.setZ( index, sparseValues[ i * itemSize + 2 ] );
            if ( itemSize >= 4 ) bufferAttribute.setW( index, sparseValues[ i * itemSize + 3 ] );
            if ( itemSize >= 5 ) throw new Error( 'THREE.GLTFLoader: Unsupported itemSize in sparse BufferAttribute.' );
  
          }
  
        }
  
        return bufferAttribute;
  
      } );
  
    }
  
    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#textures
     * @param {number} textureIndex
     * @return {Promise<THREE.Texture|null>}
     */
    loadTexture( textureIndex ) {
  
      const json = this.json;
      const options = this.options;
      const textureDef = json.textures[ textureIndex ];
      const sourceIndex = textureDef.source;
      const sourceDef = json.images[ sourceIndex ];
  
      let loader = this.textureLoader;
  
      if ( sourceDef.uri ) {
  
        const handler = options.manager.getHandler( sourceDef.uri );
        if ( handler !== null ) loader = handler;
  
      }
  
      return this.loadTextureImage( textureIndex, sourceIndex, loader );
  
    }
  
    loadTextureImage( textureIndex, sourceIndex, loader ) {
  
      const parser = this;
      const json = this.json;
  
      const textureDef = json.textures[ textureIndex ];
      const sourceDef = json.images[ sourceIndex ];
  
      const cacheKey = ( sourceDef.uri || sourceDef.bufferView ) + ':' + textureDef.sampler;
  
      if ( this.textureCache[ cacheKey ] ) {
  
        // See https://github.com/mrdoob/three.js/issues/21559.
        return this.textureCache[ cacheKey ];
  
      }
  
      const promise = this.loadImageSource( sourceIndex, loader ).then( function ( texture ) {
  
        texture.flipY = false;
  
        texture.name = textureDef.name || sourceDef.name || '';
  
        if ( texture.name === '' && typeof sourceDef.uri === 'string' && sourceDef.uri.startsWith( 'data:image/' ) === false ) {
  
          texture.name = sourceDef.uri;
  
        }
  
        const samplers = json.samplers || {};
        const sampler = samplers[ textureDef.sampler ] || {};
  
        texture.magFilter = WEBGL_FILTERS[ sampler.magFilter ] || LinearFilter;
        texture.minFilter = WEBGL_FILTERS[ sampler.minFilter ] || LinearMipmapLinearFilter;
        texture.wrapS = WEBGL_WRAPPINGS[ sampler.wrapS ] || RepeatWrapping;
        texture.wrapT = WEBGL_WRAPPINGS[ sampler.wrapT ] || RepeatWrapping;
  
        parser.associations.set( texture, { textures: textureIndex } );
  
        return texture;
  
      } ).catch( function () {
  
        return null;
  
      } );
  
      this.textureCache[ cacheKey ] = promise;
  
      return promise;
  
    }
  
    loadImageSource( sourceIndex, loader ) {
  
      const parser = this;
      const json = this.json;
      const options = this.options;
  
      if ( this.sourceCache[ sourceIndex ] !== undefined ) {
  
        return this.sourceCache[ sourceIndex ].then( ( texture ) => texture.clone() );
  
      }
  
      const sourceDef = json.images[ sourceIndex ];
  
      const URL = self.URL || self.webkitURL;
  
      let sourceURI = sourceDef.uri || '';
      let isObjectURL = false;
  
      if ( sourceDef.bufferView !== undefined ) {
  
        // Load binary image data from bufferView, if provided.
  
        sourceURI = parser.getDependency( 'bufferView', sourceDef.bufferView ).then( function ( bufferView ) {
  
          isObjectURL = true;
          const blob = new Blob( [ bufferView ], { type: sourceDef.mimeType } );
          sourceURI = URL.createObjectURL( blob );
          return sourceURI;
  
        } );
  
      } else if ( sourceDef.uri === undefined ) {
  
        throw new Error( 'THREE.GLTFLoader: Image ' + sourceIndex + ' is missing URI and bufferView' );
  
      }
  
      const promise = Promise.resolve( sourceURI ).then( function ( sourceURI ) {
  
        return new Promise( function ( resolve, reject ) {
  
          let onLoad = resolve;
  
          if ( loader.isImageBitmapLoader === true ) {
  
            onLoad = function ( imageBitmap ) {
  
              const texture = new Texture( imageBitmap );
              texture.needsUpdate = true;
  
              resolve( texture );
  
            };
  
          }
  
          loader.load( LoaderUtils.resolveURL( sourceURI, options.path ), onLoad, undefined, reject );
  
        } );
  
      } ).then( function ( texture ) {
  
        // Clean up resources and configure Texture.
  
        if ( isObjectURL === true ) {
  
          URL.revokeObjectURL( sourceURI );
  
        }
  
        texture.userData.mimeType = sourceDef.mimeType || getImageURIMimeType( sourceDef.uri );
  
        return texture;
  
      } ).catch( function ( error ) {
  
        console.error( 'THREE.GLTFLoader: Couldn\'t load texture', sourceURI );
        throw error;
  
      } );
  
      this.sourceCache[ sourceIndex ] = promise;
      return promise;
  
    }
  
    /**
     * Asynchronously assigns a texture to the given material parameters.
     * @param {Object} materialParams
     * @param {string} mapName
     * @param {Object} mapDef
     * @return {Promise<Texture>}
     */
    assignTexture( materialParams, mapName, mapDef, colorSpace ) {
  
      const parser = this;
  
      return this.getDependency( 'texture', mapDef.index ).then( function ( texture ) {
  
        if ( ! texture ) return null;
  
        if ( mapDef.texCoord !== undefined && mapDef.texCoord > 0 ) {
  
          texture = texture.clone();
          texture.channel = mapDef.texCoord;
  
        }
  
        if ( parser.extensions[ EXTENSIONS.KHR_TEXTURE_TRANSFORM ] ) {
  
          const transform = mapDef.extensions !== undefined ? mapDef.extensions[ EXTENSIONS.KHR_TEXTURE_TRANSFORM ] : undefined;
  
          if ( transform ) {
  
            const gltfReference = parser.associations.get( texture );
            texture = parser.extensions[ EXTENSIONS.KHR_TEXTURE_TRANSFORM ].extendTexture( texture, transform );
            parser.associations.set( texture, gltfReference );
  
          }
  
        }
  
        if ( colorSpace !== undefined ) {
  
          texture.colorSpace = colorSpace;
  
        }
  
        materialParams[ mapName ] = texture;
  
        return texture;
  
      } );
  
    }
  
    /**
     * Assigns final material to a Mesh, Line, or Points instance. The instance
     * already has a material (generated from the glTF material options alone)
     * but reuse of the same glTF material may require multiple threejs materials
     * to accommodate different primitive types, defines, etc. New materials will
     * be created if necessary, and reused from a cache.
     * @param  {Object3D} mesh Mesh, Line, or Points instance.
     */
    assignFinalMaterial( mesh ) {
  
      const geometry = mesh.geometry;
      let material = mesh.material;
  
      const useDerivativeTangents = geometry.attributes.tangent === undefined;
      const useVertexColors = geometry.attributes.color !== undefined;
      const useFlatShading = geometry.attributes.normal === undefined;
  
      if ( mesh.isPoints ) {
  
        const cacheKey = 'PointsMaterial:' + material.uuid;
  
        let pointsMaterial = this.cache.get( cacheKey );
  
        if ( ! pointsMaterial ) {
  
          pointsMaterial = new PointsMaterial();
          Material.prototype.copy.call( pointsMaterial, material );
          pointsMaterial.color.copy( material.color );
          pointsMaterial.map = material.map;
          pointsMaterial.sizeAttenuation = false; // glTF spec says points should be 1px
  
          this.cache.add( cacheKey, pointsMaterial );
  
        }
  
        material = pointsMaterial;
  
      } else if ( mesh.isLine ) {
  
        const cacheKey = 'LineBasicMaterial:' + material.uuid;
  
        let lineMaterial = this.cache.get( cacheKey );
  
        if ( ! lineMaterial ) {
  
          lineMaterial = new LineBasicMaterial();
          Material.prototype.copy.call( lineMaterial, material );
          lineMaterial.color.copy( material.color );
          lineMaterial.map = material.map;
  
          this.cache.add( cacheKey, lineMaterial );
  
        }
  
        material = lineMaterial;
  
      }
  
      // Clone the material if it will be modified
      if ( useDerivativeTangents || useVertexColors || useFlatShading ) {
  
        let cacheKey = 'ClonedMaterial:' + material.uuid + ':';
  
        if ( useDerivativeTangents ) cacheKey += 'derivative-tangents:';
        if ( useVertexColors ) cacheKey += 'vertex-colors:';
        if ( useFlatShading ) cacheKey += 'flat-shading:';
  
        let cachedMaterial = this.cache.get( cacheKey );
  
        if ( ! cachedMaterial ) {
  
          cachedMaterial = material.clone();
  
          if ( useVertexColors ) cachedMaterial.vertexColors = true;
          if ( useFlatShading ) cachedMaterial.flatShading = true;
  
          if ( useDerivativeTangents ) {
  
            // https://github.com/mrdoob/three.js/issues/11438#issuecomment-507003995
            if ( cachedMaterial.normalScale ) cachedMaterial.normalScale.y *= - 1;
            if ( cachedMaterial.clearcoatNormalScale ) cachedMaterial.clearcoatNormalScale.y *= - 1;
  
          }
  
          this.cache.add( cacheKey, cachedMaterial );
  
          this.associations.set( cachedMaterial, this.associations.get( material ) );
  
        }
  
        material = cachedMaterial;
  
      }
  
      mesh.material = material;
  
    }
  
    getMaterialType( /* materialIndex */ ) {
  
      return MeshStandardMaterial;
  
    }
  
    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#materials
     * @param {number} materialIndex
     * @return {Promise<Material>}
     */
    loadMaterial( materialIndex ) {
  
      const parser = this;
      const json = this.json;
      const extensions = this.extensions;
      const materialDef = json.materials[ materialIndex ];
  
      let materialType;
      const materialParams = {};
      const materialExtensions = materialDef.extensions || {};
  
      const pending = [];
  
      if ( materialExtensions[ EXTENSIONS.KHR_MATERIALS_UNLIT ] ) {
  
        const kmuExtension = extensions[ EXTENSIONS.KHR_MATERIALS_UNLIT ];
        materialType = kmuExtension.getMaterialType();
        pending.push( kmuExtension.extendParams( materialParams, materialDef, parser ) );
  
      } else {
  
        // Specification:
        // https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#metallic-roughness-material
  
        const metallicRoughness = materialDef.pbrMetallicRoughness || {};
  
        materialParams.color = new Color( 1.0, 1.0, 1.0 );
        materialParams.opacity = 1.0;
  
        if ( Array.isArray( metallicRoughness.baseColorFactor ) ) {
  
          const array = metallicRoughness.baseColorFactor;
  
          materialParams.color.setRGB( array[ 0 ], array[ 1 ], array[ 2 ], LinearSRGBColorSpace );
          materialParams.opacity = array[ 3 ];
  
        }
  
        if ( metallicRoughness.baseColorTexture !== undefined ) {
  
          pending.push( parser.assignTexture( materialParams, 'map', metallicRoughness.baseColorTexture, SRGBColorSpace ) );
  
        }
  
        materialParams.metalness = metallicRoughness.metallicFactor !== undefined ? metallicRoughness.metallicFactor : 1.0;
        materialParams.roughness = metallicRoughness.roughnessFactor !== undefined ? metallicRoughness.roughnessFactor : 1.0;
  
        if ( metallicRoughness.metallicRoughnessTexture !== undefined ) {
  
          pending.push( parser.assignTexture( materialParams, 'metalnessMap', metallicRoughness.metallicRoughnessTexture ) );
          pending.push( parser.assignTexture( materialParams, 'roughnessMap', metallicRoughness.metallicRoughnessTexture ) );
  
        }
  
        materialType = this._invokeOne( function ( ext ) {
  
          return ext.getMaterialType && ext.getMaterialType( materialIndex );
  
        } );
  
        pending.push( Promise.all( this._invokeAll( function ( ext ) {
  
          return ext.extendMaterialParams && ext.extendMaterialParams( materialIndex, materialParams );
  
        } ) ) );
  
      }
  
      if ( materialDef.doubleSided === true ) {
  
        materialParams.side = DoubleSide;
  
      }
  
      const alphaMode = materialDef.alphaMode || ALPHA_MODES.OPAQUE;
  
      if ( alphaMode === ALPHA_MODES.BLEND ) {
  
        materialParams.transparent = true;
  
        // See: https://github.com/mrdoob/three.js/issues/17706
        materialParams.depthWrite = false;
  
      } else {
  
        materialParams.transparent = false;
  
        if ( alphaMode === ALPHA_MODES.MASK ) {
  
          materialParams.alphaTest = materialDef.alphaCutoff !== undefined ? materialDef.alphaCutoff : 0.5;
  
        }
  
      }
  
      if ( materialDef.normalTexture !== undefined && materialType !== MeshBasicMaterial ) {
  
        pending.push( parser.assignTexture( materialParams, 'normalMap', materialDef.normalTexture ) );
  
        materialParams.normalScale = new Vector2( 1, 1 );
  
        if ( materialDef.normalTexture.scale !== undefined ) {
  
          const scale = materialDef.normalTexture.scale;
  
          materialParams.normalScale.set( scale, scale );
  
        }
  
      }
  
      if ( materialDef.occlusionTexture !== undefined && materialType !== MeshBasicMaterial ) {
  
        pending.push( parser.assignTexture( materialParams, 'aoMap', materialDef.occlusionTexture ) );
  
        if ( materialDef.occlusionTexture.strength !== undefined ) {
  
          materialParams.aoMapIntensity = materialDef.occlusionTexture.strength;
  
        }
  
      }
  
      if ( materialDef.emissiveFactor !== undefined && materialType !== MeshBasicMaterial ) {
  
        const emissiveFactor = materialDef.emissiveFactor;
        materialParams.emissive = new Color().setRGB( emissiveFactor[ 0 ], emissiveFactor[ 1 ], emissiveFactor[ 2 ], LinearSRGBColorSpace );
  
      }
  
      if ( materialDef.emissiveTexture !== undefined && materialType !== MeshBasicMaterial ) {
  
        pending.push( parser.assignTexture( materialParams, 'emissiveMap', materialDef.emissiveTexture, SRGBColorSpace ) );
  
      }
  
      return Promise.all( pending ).then( function () {
  
        const material = new materialType( materialParams );
  
        if ( materialDef.name ) material.name = materialDef.name;
  
        assignExtrasToUserData( material, materialDef );
  
        parser.associations.set( material, { materials: materialIndex } );
  
        if ( materialDef.extensions ) addUnknownExtensionsToUserData( extensions, material, materialDef );
  
        return material;
  
      } );
  
    }
  
    /** When Object3D instances are targeted by animation, they need unique names. */
    createUniqueName( originalName ) {
  
      const sanitizedName = PropertyBinding.sanitizeNodeName( originalName || '' );
  
      if ( sanitizedName in this.nodeNamesUsed ) {
  
        return sanitizedName + '_' + ( ++ this.nodeNamesUsed[ sanitizedName ] );
  
      } else {
  
        this.nodeNamesUsed[ sanitizedName ] = 0;
  
        return sanitizedName;
  
      }
  
    }
  
    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#geometry
     *
     * Creates BufferGeometries from primitives.
     *
     * @param {Array<GLTF.Primitive>} primitives
     * @return {Promise<Array<BufferGeometry>>}
     */
    loadGeometries( primitives ) {
  
      const parser = this;
      const extensions = this.extensions;
      const cache = this.primitiveCache;
  
      function createDracoPrimitive( primitive ) {
  
        return extensions[ EXTENSIONS.KHR_DRACO_MESH_COMPRESSION ]
          .decodePrimitive( primitive, parser )
          .then( function ( geometry ) {
  
            return addPrimitiveAttributes( geometry, primitive, parser );
  
          } );
  
      }
  
      const pending = [];
  
      for ( let i = 0, il = primitives.length; i < il; i ++ ) {
  
        const primitive = primitives[ i ];
        const cacheKey = createPrimitiveKey( primitive );
  
        // See if we've already created this geometry
        const cached = cache[ cacheKey ];
  
        if ( cached ) {
  
          // Use the cached geometry if it exists
          pending.push( cached.promise );
  
        } else {
  
          let geometryPromise;
  
          if ( primitive.extensions && primitive.extensions[ EXTENSIONS.KHR_DRACO_MESH_COMPRESSION ] ) {
  
            // Use DRACO geometry if available
            geometryPromise = createDracoPrimitive( primitive );
  
          } else {
  
            // Otherwise create a new geometry
            geometryPromise = addPrimitiveAttributes( new BufferGeometry(), primitive, parser );
  
          }
  
          // Cache this geometry
          cache[ cacheKey ] = { primitive: primitive, promise: geometryPromise };
  
          pending.push( geometryPromise );
  
        }
  
      }
  
      return Promise.all( pending );
  
    }
  
    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#meshes
     * @param {number} meshIndex
     * @return {Promise<Group|Mesh|SkinnedMesh>}
     */
    loadMesh( meshIndex ) {
  
      const parser = this;
      const json = this.json;
      const extensions = this.extensions;
  
      const meshDef = json.meshes[ meshIndex ];
      const primitives = meshDef.primitives;
  
      const pending = [];
  
      for ( let i = 0, il = primitives.length; i < il; i ++ ) {
  
        const material = primitives[ i ].material === undefined
          ? createDefaultMaterial( this.cache )
          : this.getDependency( 'material', primitives[ i ].material );
  
        pending.push( material );
  
      }
  
      pending.push( parser.loadGeometries( primitives ) );
  
      return Promise.all( pending ).then( function ( results ) {
  
        const materials = results.slice( 0, results.length - 1 );
        const geometries = results[ results.length - 1 ];
  
        const meshes = [];
  
        for ( let i = 0, il = geometries.length; i < il; i ++ ) {
  
          const geometry = geometries[ i ];
          const primitive = primitives[ i ];
  
          // 1. create Mesh
  
          let mesh;
  
          const material = materials[ i ];
  
          if ( primitive.mode === WEBGL_CONSTANTS.TRIANGLES ||
              primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP ||
              primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN ||
              primitive.mode === undefined ) {
  
            // .isSkinnedMesh isn't in glTF spec. See ._markDefs()
            mesh = meshDef.isSkinnedMesh === true
              ? new SkinnedMesh( geometry, material )
              : new Mesh( geometry, material );
  
            if ( mesh.isSkinnedMesh === true ) {
  
              // normalize skin weights to fix malformed assets (see #15319)
              mesh.normalizeSkinWeights();
  
            }
  
            if ( primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP ) {
  
              mesh.geometry = toTrianglesDrawMode( mesh.geometry, TriangleStripDrawMode );
  
            } else if ( primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN ) {
  
              mesh.geometry = toTrianglesDrawMode( mesh.geometry, TriangleFanDrawMode );
  
            }
  
          } else if ( primitive.mode === WEBGL_CONSTANTS.LINES ) {
  
            mesh = new LineSegments( geometry, material );
  
          } else if ( primitive.mode === WEBGL_CONSTANTS.LINE_STRIP ) {
  
            mesh = new Line( geometry, material );
  
          } else if ( primitive.mode === WEBGL_CONSTANTS.LINE_LOOP ) {
  
            mesh = new LineLoop( geometry, material );
  
          } else if ( primitive.mode === WEBGL_CONSTANTS.POINTS ) {
  
            mesh = new Points( geometry, material );
  
          } else {
  
            throw new Error( 'THREE.GLTFLoader: Primitive mode unsupported: ' + primitive.mode );
  
          }
  
          if ( Object.keys( mesh.geometry.morphAttributes ).length > 0 ) {
  
            updateMorphTargets( mesh, meshDef );
  
          }
  
          mesh.name = parser.createUniqueName( meshDef.name || ( 'mesh_' + meshIndex ) );
  
          assignExtrasToUserData( mesh, meshDef );
  
          if ( primitive.extensions ) addUnknownExtensionsToUserData( extensions, mesh, primitive );
  
          parser.assignFinalMaterial( mesh );
  
          meshes.push( mesh );
  
        }
  
        for ( let i = 0, il = meshes.length; i < il; i ++ ) {
  
          parser.associations.set( meshes[ i ], {
            meshes: meshIndex,
            primitives: i
          } );
  
        }
  
        if ( meshes.length === 1 ) {
  
          if ( meshDef.extensions ) addUnknownExtensionsToUserData( extensions, meshes[ 0 ], meshDef );
  
          return meshes[ 0 ];
  
        }
  
        const group = new Group();
  
        if ( meshDef.extensions ) addUnknownExtensionsToUserData( extensions, group, meshDef );
  
        parser.associations.set( group, { meshes: meshIndex } );
  
        for ( let i = 0, il = meshes.length; i < il; i ++ ) {
  
          group.add( meshes[ i ] );
  
        }
  
        return group;
  
      } );
  
    }
  
    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#cameras
     * @param {number} cameraIndex
     * @return {Promise<THREE.Camera>}
     */
    loadCamera( cameraIndex ) {
  
      let camera;
      const cameraDef = this.json.cameras[ cameraIndex ];
      const params = cameraDef[ cameraDef.type ];
  
      if ( ! params ) {
  
        console.warn( 'THREE.GLTFLoader: Missing camera parameters.' );
        return;
  
      }
  
      if ( cameraDef.type === 'perspective' ) {
  
        camera = new PerspectiveCamera( MathUtils.radToDeg( params.yfov ), params.aspectRatio || 1, params.znear || 1, params.zfar || 2e6 );
  
      } else if ( cameraDef.type === 'orthographic' ) {
  
        camera = new OrthographicCamera( - params.xmag, params.xmag, params.ymag, - params.ymag, params.znear, params.zfar );
  
      }
  
      if ( cameraDef.name ) camera.name = this.createUniqueName( cameraDef.name );
  
      assignExtrasToUserData( camera, cameraDef );
  
      return Promise.resolve( camera );
  
    }
  
    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#skins
     * @param {number} skinIndex
     * @return {Promise<Skeleton>}
     */
    loadSkin( skinIndex ) {
  
      const skinDef = this.json.skins[ skinIndex ];
  
      const pending = [];
  
      for ( let i = 0, il = skinDef.joints.length; i < il; i ++ ) {
  
        pending.push( this._loadNodeShallow( skinDef.joints[ i ] ) );
  
      }
  
      if ( skinDef.inverseBindMatrices !== undefined ) {
  
        pending.push( this.getDependency( 'accessor', skinDef.inverseBindMatrices ) );
  
      } else {
  
        pending.push( null );
  
      }
  
      return Promise.all( pending ).then( function ( results ) {
  
        const inverseBindMatrices = results.pop();
        const jointNodes = results;
  
        // Note that bones (joint nodes) may or may not be in the
        // scene graph at this time.
  
        const bones = [];
        const boneInverses = [];
  
        for ( let i = 0, il = jointNodes.length; i < il; i ++ ) {
  
          const jointNode = jointNodes[ i ];
  
          if ( jointNode ) {
  
            bones.push( jointNode );
  
            const mat = new Matrix4();
  
            if ( inverseBindMatrices !== null ) {
  
              mat.fromArray( inverseBindMatrices.array, i * 16 );
  
            }
  
            boneInverses.push( mat );
  
          } else {
  
            console.warn( 'THREE.GLTFLoader: Joint "%s" could not be found.', skinDef.joints[ i ] );
  
          }
  
        }
  
        return new Skeleton( bones, boneInverses );
  
      } );
  
    }
  
    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#animations
     * @param {number} animationIndex
     * @return {Promise<AnimationClip>}
     */
    loadAnimation( animationIndex ) {
  
      const json = this.json;
      const parser = this;
  
      const animationDef = json.animations[ animationIndex ];
      const animationName = animationDef.name ? animationDef.name : 'animation_' + animationIndex;
  
      const pendingNodes = [];
      const pendingInputAccessors = [];
      const pendingOutputAccessors = [];
      const pendingSamplers = [];
      const pendingTargets = [];
  
      for ( let i = 0, il = animationDef.channels.length; i < il; i ++ ) {
  
        const channel = animationDef.channels[ i ];
        const sampler = animationDef.samplers[ channel.sampler ];
        const target = channel.target;
        const name = target.node;
        const input = animationDef.parameters !== undefined ? animationDef.parameters[ sampler.input ] : sampler.input;
        const output = animationDef.parameters !== undefined ? animationDef.parameters[ sampler.output ] : sampler.output;
  
        if ( target.node === undefined ) continue;
  
        pendingNodes.push( this.getDependency( 'node', name ) );
        pendingInputAccessors.push( this.getDependency( 'accessor', input ) );
        pendingOutputAccessors.push( this.getDependency( 'accessor', output ) );
        pendingSamplers.push( sampler );
        pendingTargets.push( target );
  
      }
  
      return Promise.all( [
  
        Promise.all( pendingNodes ),
        Promise.all( pendingInputAccessors ),
        Promise.all( pendingOutputAccessors ),
        Promise.all( pendingSamplers ),
        Promise.all( pendingTargets )
  
      ] ).then( function ( dependencies ) {
  
        const nodes = dependencies[ 0 ];
        const inputAccessors = dependencies[ 1 ];
        const outputAccessors = dependencies[ 2 ];
        const samplers = dependencies[ 3 ];
        const targets = dependencies[ 4 ];
  
        const tracks = [];
  
        for ( let i = 0, il = nodes.length; i < il; i ++ ) {
  
          const node = nodes[ i ];
          const inputAccessor = inputAccessors[ i ];
          const outputAccessor = outputAccessors[ i ];
          const sampler = samplers[ i ];
          const target = targets[ i ];
  
          if ( node === undefined ) continue;
  
          if ( node.updateMatrix ) {
  
            node.updateMatrix();
  
          }
  
          const createdTracks = parser._createAnimationTracks( node, inputAccessor, outputAccessor, sampler, target );
  
          if ( createdTracks ) {
  
            for ( let k = 0; k < createdTracks.length; k ++ ) {
  
              tracks.push( createdTracks[ k ] );
  
            }
  
          }
  
        }
  
        return new AnimationClip( animationName, undefined, tracks );
  
      } );
  
    }
  
    createNodeMesh( nodeIndex ) {
  
      const json = this.json;
      const parser = this;
      const nodeDef = json.nodes[ nodeIndex ];
  
      if ( nodeDef.mesh === undefined ) return null;
  
      return parser.getDependency( 'mesh', nodeDef.mesh ).then( function ( mesh ) {
  
        const node = parser._getNodeRef( parser.meshCache, nodeDef.mesh, mesh );
  
        // if weights are provided on the node, override weights on the mesh.
        if ( nodeDef.weights !== undefined ) {
  
          node.traverse( function ( o ) {
  
            if ( ! o.isMesh ) return;
  
            for ( let i = 0, il = nodeDef.weights.length; i < il; i ++ ) {
  
              o.morphTargetInfluences[ i ] = nodeDef.weights[ i ];
  
            }
  
          } );
  
        }
  
        return node;
  
      } );
  
    }
  
    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#nodes-and-hierarchy
     * @param {number} nodeIndex
     * @return {Promise<Object3D>}
     */
    loadNode( nodeIndex ) {
  
      const json = this.json;
      const parser = this;
  
      const nodeDef = json.nodes[ nodeIndex ];
  
      const nodePending = parser._loadNodeShallow( nodeIndex );
  
      const childPending = [];
      const childrenDef = nodeDef.children || [];
  
      for ( let i = 0, il = childrenDef.length; i < il; i ++ ) {
  
        childPending.push( parser.getDependency( 'node', childrenDef[ i ] ) );
  
      }
  
      const skeletonPending = nodeDef.skin === undefined
        ? Promise.resolve( null )
        : parser.getDependency( 'skin', nodeDef.skin );
  
      return Promise.all( [
        nodePending,
        Promise.all( childPending ),
        skeletonPending
      ] ).then( function ( results ) {
  
        const node = results[ 0 ];
        const children = results[ 1 ];
        const skeleton = results[ 2 ];
  
        if ( skeleton !== null ) {
  
          // This full traverse should be fine because
          // child glTF nodes have not been added to this node yet.
          node.traverse( function ( mesh ) {
  
            if ( ! mesh.isSkinnedMesh ) return;
  
            mesh.bind( skeleton, _identityMatrix );
  
          } );
  
        }
  
        for ( let i = 0, il = children.length; i < il; i ++ ) {
  
          node.add( children[ i ] );
  
        }
  
        return node;
  
      } );
  
    }
  
    // ._loadNodeShallow() parses a single node.
    // skin and child nodes are created and added in .loadNode() (no '_' prefix).
    _loadNodeShallow( nodeIndex ) {
  
      const json = this.json;
      const extensions = this.extensions;
      const parser = this;
  
      // This method is called from .loadNode() and .loadSkin().
      // Cache a node to avoid duplication.
  
      if ( this.nodeCache[ nodeIndex ] !== undefined ) {
  
        return this.nodeCache[ nodeIndex ];
  
      }
  
      const nodeDef = json.nodes[ nodeIndex ];
  
      // reserve node's name before its dependencies, so the root has the intended name.
      const nodeName = nodeDef.name ? parser.createUniqueName( nodeDef.name ) : '';
  
      const pending = [];
  
      const meshPromise = parser._invokeOne( function ( ext ) {
  
        return ext.createNodeMesh && ext.createNodeMesh( nodeIndex );
  
      } );
  
      if ( meshPromise ) {
  
        pending.push( meshPromise );
  
      }
  
      if ( nodeDef.camera !== undefined ) {
  
        pending.push( parser.getDependency( 'camera', nodeDef.camera ).then( function ( camera ) {
  
          return parser._getNodeRef( parser.cameraCache, nodeDef.camera, camera );
  
        } ) );
  
      }
  
      parser._invokeAll( function ( ext ) {
  
        return ext.createNodeAttachment && ext.createNodeAttachment( nodeIndex );
  
      } ).forEach( function ( promise ) {
  
        pending.push( promise );
  
      } );
  
      this.nodeCache[ nodeIndex ] = Promise.all( pending ).then( function ( objects ) {
  
        let node;
  
        // .isBone isn't in glTF spec. See ._markDefs
        if ( nodeDef.isBone === true ) {
  
          node = new Bone();
  
        } else if ( objects.length > 1 ) {
  
          node = new Group();
  
        } else if ( objects.length === 1 ) {
  
          node = objects[ 0 ];
  
        } else {
  
          node = new Object3D();
  
        }
  
        if ( node !== objects[ 0 ] ) {
  
          for ( let i = 0, il = objects.length; i < il; i ++ ) {
  
            node.add( objects[ i ] );
  
          }
  
        }
  
        if ( nodeDef.name ) {
  
          node.userData.name = nodeDef.name;
          node.name = nodeName;
  
        }
  
        assignExtrasToUserData( node, nodeDef );
  
        if ( nodeDef.extensions ) addUnknownExtensionsToUserData( extensions, node, nodeDef );
  
        if ( nodeDef.matrix !== undefined ) {
  
          const matrix = new Matrix4();
          matrix.fromArray( nodeDef.matrix );
          node.applyMatrix4( matrix );
  
        } else {
  
          if ( nodeDef.translation !== undefined ) {
  
            node.position.fromArray( nodeDef.translation );
  
          }
  
          if ( nodeDef.rotation !== undefined ) {
  
            node.quaternion.fromArray( nodeDef.rotation );
  
          }
  
          if ( nodeDef.scale !== undefined ) {
  
            node.scale.fromArray( nodeDef.scale );
  
          }
  
        }
  
        if ( ! parser.associations.has( node ) ) {
  
          parser.associations.set( node, {} );
  
        }
  
        parser.associations.get( node ).nodes = nodeIndex;
  
        return node;
  
      } );
  
      return this.nodeCache[ nodeIndex ];
  
    }
  
    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#scenes
     * @param {number} sceneIndex
     * @return {Promise<Group>}
     */
    loadScene( sceneIndex ) {
  
      const extensions = this.extensions;
      const sceneDef = this.json.scenes[ sceneIndex ];
      const parser = this;
  
      // Loader returns Group, not Scene.
      // See: https://github.com/mrdoob/three.js/issues/18342#issuecomment-578981172
      const scene = new Group();
      if ( sceneDef.name ) scene.name = parser.createUniqueName( sceneDef.name );
  
      assignExtrasToUserData( scene, sceneDef );
  
      if ( sceneDef.extensions ) addUnknownExtensionsToUserData( extensions, scene, sceneDef );
  
      const nodeIds = sceneDef.nodes || [];
  
      const pending = [];
  
      for ( let i = 0, il = nodeIds.length; i < il; i ++ ) {
  
        pending.push( parser.getDependency( 'node', nodeIds[ i ] ) );
  
      }
  
      return Promise.all( pending ).then( function ( nodes ) {
  
        for ( let i = 0, il = nodes.length; i < il; i ++ ) {
  
          scene.add( nodes[ i ] );
  
        }
  
        // Removes dangling associations, associations that reference a node that
        // didn't make it into the scene.
        const reduceAssociations = ( node ) => {
  
          const reducedAssociations = new Map();
  
          for ( const [ key, value ] of parser.associations ) {
  
            if ( key instanceof Material || key instanceof Texture ) {
  
              reducedAssociations.set( key, value );
  
            }
  
          }
  
          node.traverse( ( node ) => {
  
            const mappings = parser.associations.get( node );
  
            if ( mappings != null ) {
  
              reducedAssociations.set( node, mappings );
  
            }
  
          } );
  
          return reducedAssociations;
  
        };
  
        parser.associations = reduceAssociations( scene );
  
        return scene;
  
      } );
  
    }
  
    _createAnimationTracks( node, inputAccessor, outputAccessor, sampler, target ) {
  
      const tracks = [];
  
      const targetName = node.name ? node.name : node.uuid;
      const targetNames = [];
  
      if ( PATH_PROPERTIES[ target.path ] === PATH_PROPERTIES.weights ) {
  
        node.traverse( function ( object ) {
  
          if ( object.morphTargetInfluences ) {
  
            targetNames.push( object.name ? object.name : object.uuid );
  
          }
  
        } );
  
      } else {
  
        targetNames.push( targetName );
  
      }
  
      let TypedKeyframeTrack;
  
      switch ( PATH_PROPERTIES[ target.path ] ) {
  
        case PATH_PROPERTIES.weights:
  
          TypedKeyframeTrack = NumberKeyframeTrack;
          break;
  
        case PATH_PROPERTIES.rotation:
  
          TypedKeyframeTrack = QuaternionKeyframeTrack;
          break;
  
        case PATH_PROPERTIES.position:
        case PATH_PROPERTIES.scale:
  
          TypedKeyframeTrack = VectorKeyframeTrack;
          break;
  
        default:
  
          switch ( outputAccessor.itemSize ) {
  
            case 1:
              TypedKeyframeTrack = NumberKeyframeTrack;
              break;
            case 2:
            case 3:
            default:
              TypedKeyframeTrack = VectorKeyframeTrack;
              break;
  
          }
  
          break;
  
      }
  
      const interpolation = sampler.interpolation !== undefined ? INTERPOLATION[ sampler.interpolation ] : InterpolateLinear;
  
  
      const outputArray = this._getArrayFromAccessor( outputAccessor );
  
      for ( let j = 0, jl = targetNames.length; j < jl; j ++ ) {
  
        const track = new TypedKeyframeTrack(
          targetNames[ j ] + '.' + PATH_PROPERTIES[ target.path ],
          inputAccessor.array,
          outputArray,
          interpolation
        );
  
        // Override interpolation with custom factory method.
        if ( sampler.interpolation === 'CUBICSPLINE' ) {
  
          this._createCubicSplineTrackInterpolant( track );
  
        }
  
        tracks.push( track );
  
      }
  
      return tracks;
  
    }
  
    _getArrayFromAccessor( accessor ) {
  
      let outputArray = accessor.array;
  
      if ( accessor.normalized ) {
  
        const scale = getNormalizedComponentScale( outputArray.constructor );
        const scaled = new Float32Array( outputArray.length );
  
        for ( let j = 0, jl = outputArray.length; j < jl; j ++ ) {
  
          scaled[ j ] = outputArray[ j ] * scale;
  
        }
  
        outputArray = scaled;
  
      }
  
      return outputArray;
  
    }
  
    _createCubicSplineTrackInterpolant( track ) {
  
      track.createInterpolant = function InterpolantFactoryMethodGLTFCubicSpline( result ) {
  
        // A CUBICSPLINE keyframe in glTF has three output values for each input value,
        // representing inTangent, splineVertex, and outTangent. As a result, track.getValueSize()
        // must be divided by three to get the interpolant's sampleSize argument.
  
        const interpolantType = ( this instanceof QuaternionKeyframeTrack ) ? GLTFCubicSplineQuaternionInterpolant : GLTFCubicSplineInterpolant;
  
        return new interpolantType( this.times, this.values, this.getValueSize() / 3, result );
  
      };
  
      // Mark as CUBICSPLINE. `track.getInterpolation()` doesn't support custom interpolants.
      track.createInterpolant.isInterpolantFactoryMethodGLTFCubicSpline = true;
  
    }
  
  }
  
  /**
   * @param {BufferGeometry} geometry
   * @param {GLTF.Primitive} primitiveDef
   * @param {GLTFParser} parser
   */
  function computeBounds( geometry, primitiveDef, parser ) {
  
    const attributes = primitiveDef.attributes;
  
    const box = new Box3();
  
    if ( attributes.POSITION !== undefined ) {
  
      const accessor = parser.json.accessors[ attributes.POSITION ];
  
      const min = accessor.min;
      const max = accessor.max;
  
      // glTF requires 'min' and 'max', but VRM (which extends glTF) currently ignores that requirement.
  
      if ( min !== undefined && max !== undefined ) {
  
        box.set(
          new Vector3( min[ 0 ], min[ 1 ], min[ 2 ] ),
          new Vector3( max[ 0 ], max[ 1 ], max[ 2 ] )
        );
  
        if ( accessor.normalized ) {
  
          const boxScale = getNormalizedComponentScale( WEBGL_COMPONENT_TYPES[ accessor.componentType ] );
          box.min.multiplyScalar( boxScale );
          box.max.multiplyScalar( boxScale );
  
        }
  
      } else {
  
        console.warn( 'THREE.GLTFLoader: Missing min/max properties for accessor POSITION.' );
  
        return;
  
      }
  
    } else {
  
      return;
  
    }
  
    const targets = primitiveDef.targets;
  
    if ( targets !== undefined ) {
  
      const maxDisplacement = new Vector3();
      const vector = new Vector3();
  
      for ( let i = 0, il = targets.length; i < il; i ++ ) {
  
        const target = targets[ i ];
  
        if ( target.POSITION !== undefined ) {
  
          const accessor = parser.json.accessors[ target.POSITION ];
          const min = accessor.min;
          const max = accessor.max;
  
          // glTF requires 'min' and 'max', but VRM (which extends glTF) currently ignores that requirement.
  
          if ( min !== undefined && max !== undefined ) {
  
            // we need to get max of absolute components because target weight is [-1,1]
            vector.setX( Math.max( Math.abs( min[ 0 ] ), Math.abs( max[ 0 ] ) ) );
            vector.setY( Math.max( Math.abs( min[ 1 ] ), Math.abs( max[ 1 ] ) ) );
            vector.setZ( Math.max( Math.abs( min[ 2 ] ), Math.abs( max[ 2 ] ) ) );
  
  
            if ( accessor.normalized ) {
  
              const boxScale = getNormalizedComponentScale( WEBGL_COMPONENT_TYPES[ accessor.componentType ] );
              vector.multiplyScalar( boxScale );
  
            }
  
            // Note: this assumes that the sum of all weights is at most 1. This isn't quite correct - it's more conservative
            // to assume that each target can have a max weight of 1. However, for some use cases - notably, when morph targets
            // are used to implement key-frame animations and as such only two are active at a time - this results in very large
            // boxes. So for now we make a box that's sometimes a touch too small but is hopefully mostly of reasonable size.
            maxDisplacement.max( vector );
  
          } else {
  
            console.warn( 'THREE.GLTFLoader: Missing min/max properties for accessor POSITION.' );
  
          }
  
        }
  
      }
  
      // As per comment above this box isn't conservative, but has a reasonable size for a very large number of morph targets.
      box.expandByVector( maxDisplacement );
  
    }
  
    geometry.boundingBox = box;
  
    const sphere = new Sphere();
  
    box.getCenter( sphere.center );
    sphere.radius = box.min.distanceTo( box.max ) / 2;
  
    geometry.boundingSphere = sphere;
  
  }
  
  /**
   * @param {BufferGeometry} geometry
   * @param {GLTF.Primitive} primitiveDef
   * @param {GLTFParser} parser
   * @return {Promise<BufferGeometry>}
   */
  function addPrimitiveAttributes( geometry, primitiveDef, parser ) {
  
    const attributes = primitiveDef.attributes;
  
    const pending = [];
  
    function assignAttributeAccessor( accessorIndex, attributeName ) {
  
      return parser.getDependency( 'accessor', accessorIndex )
        .then( function ( accessor ) {
  
          geometry.setAttribute( attributeName, accessor );
  
        } );
  
    }
  
    for ( const gltfAttributeName in attributes ) {
  
      const threeAttributeName = ATTRIBUTES[ gltfAttributeName ] || gltfAttributeName.toLowerCase();
  
      // Skip attributes already provided by e.g. Draco extension.
      if ( threeAttributeName in geometry.attributes ) continue;
  
      pending.push( assignAttributeAccessor( attributes[ gltfAttributeName ], threeAttributeName ) );
  
    }
  
    if ( primitiveDef.indices !== undefined && ! geometry.index ) {
  
      const accessor = parser.getDependency( 'accessor', primitiveDef.indices ).then( function ( accessor ) {
  
        geometry.setIndex( accessor );
  
      } );
  
      pending.push( accessor );
  
    }
  
    if ( ColorManagement.workingColorSpace !== LinearSRGBColorSpace && 'COLOR_0' in attributes ) {
  
      console.warn( `THREE.GLTFLoader: Converting vertex colors from "srgb-linear" to "${ColorManagement.workingColorSpace}" not supported.` );
  
    }
  
    assignExtrasToUserData( geometry, primitiveDef );
  
    computeBounds( geometry, primitiveDef, parser );
  
    return Promise.all( pending ).then( function () {
  
      return primitiveDef.targets !== undefined
        ? addMorphTargets( geometry, primitiveDef.targets, parser )
        : geometry;
  
    } );
  
  }
  
  export { GLTFLoader };
  